Always warn when 'cabal install' cannot find a dependency #2853
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This commit prevents cabal from filtering out messages about missing packages when summarizing the solver trace.
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Looking at this now ... |
| go v l (Failure c fr : ms) = (atLevel v l $ "fail" ++ showFR c fr) (go v l ms) | ||
| go v l (Failure c fr : ms) = (atLevel v l $ showFailure c fr) (go v l ms) | ||
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| showPackageGoal qpn gr = "next goal: " ++ showQPN qpn ++ showGRs gr |
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I somewhat prefer if local functions have type signatures, too.
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Thanks a lot for this. I have some minor questions, but I'm in principle in favour of this to go in as soon as possible. |
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@kosmikus I added the type signatures and a comment. I can combine the commits if you want. |
kosmikus
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Oct 13, 2015
Always warn when 'cabal install' cannot find a dependency
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Thanks again. |
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Thanks! |
grayjay
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to grayjay/cabal
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Jan 8, 2018
…kell#4823). This commit changes the way that the solver generates the summarized log that it displays at normal verbosity. Previously, the solver saved the full log from the start to the first backjump. Then it filtered the log using the conflict set from the node where the first backjump occurred, i.e., it removed all lines from the log that did not relate to variables in the conflict set. The solver also printed the final conflict set at the end of the log. This approach had several problems: 1. It was possible for the conflicts at the first backjump to be completely unrelated to the final conflict set (issue haskell#941). The conflicts in the summarized log could be irrelevant to the failure, for example, if they were introduced by only a single version of a dependency, which the solver could easily skip, and the real problem was a different dependency that was missing from the index. Even if the summarized log was relevant, but different from the final conflict set, it was confusing to show two different explanations for the same failure. 2. Filtering the full log was error prone and could easily remove lines relevant to the conflict set. It caused bugs mentioned in haskell#2853 and haskell#4154. 3. The conflict set at the first backjump contains the variables directly involved in the conflicts at that level and the variables that introduced them, but it doesn't contain the whole chain of variables starting with the user targets. When the log is filtered with that conflict set, it can be unclear why the solver needed to choose those packages in the first place. This commit creates the summarized log by rerunning the solver with a backjump limit of zero and using the full log. Using the full log avoids (2) and (3). However, it is also important to shorten the log by only showing choices that are relevant to conflicts. This commit uses different approaches for the two types of failure. No solution: This commit makes the solver prefer variables from the final conflict set from the first run when choosing goals in the second run. This means that the log to the first backjump should only mention packages, flags, and stanzas from the final conflict set. (The solver shouldn't need to choose any other packages, because, for every variable in the final conflict set, the final conflict set should also contain the variable that introduced that variable. The solver can follow that chain of variables in reverse order from the user target to the conflict.) Backjump limit reached: There is no final conflict set in this case, since the solver didn't search the whole tree. This commit tries to create a final conflict set by rerunning the solver with a subtree of the original search tree that contains the path to the first backjump. Then it uses the final conflict set as above. Here is an example of the differences between the new and old logs, from haskell#4792, using GHC 8.2.1: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: contravariant (dependency of thorn) [__1] rejecting: contravariant-1.4, contravariant-1.3.3, contravariant-1.3.2, contravariant-1.3.1.1, contravariant-1.3.1, contravariant-1.3, contravariant-1.2.2.1, contravariant-1.2.2, contravariant-1.2.1, contravariant-1.2.0.1, contravariant-1.2, contravariant-1.1, contravariant-1.0 (conflict: thorn => contravariant<1) [__1] trying: contravariant-0.6.1.1 [__2] next goal: transformers (dependency of contravariant) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: contravariant => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn Differences: - The new summary has level numbers, like the full log. - The conflicts are different. The old log mentions thorn, base, profunctors, and transformers, and the new log mentions the four packages from the conflict set: thorn, contravariant, transformers, and base. - The new log starts with the solver choosing a user goal, thorn. The solver continues to display the conflicts at the first backjump when it reaches the backjump limit, i.e, it shows profunctors instead of contravariant. The goal order differs, though: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: profunctors (dependency of thorn) [__1] rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) [__1] trying: profunctors-4.4.1 [__2] next goal: transformers (dependency of profunctors) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). One downside of this change is that the solver may reach the backjump limit when generating the summarized log, if the backjump limit is small: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=1 Resolving dependencies... cabal: Backjump limit reached (currently 1, change with --max-backjumps or try to run with --reorder-goals). Failed to generate a summarized dependency solver log due to low backjump limit. Another downside is the performance impact of rerunning the solver.
grayjay
added a commit
to grayjay/cabal
that referenced
this pull request
Jan 8, 2018
…kell#4823). This commit changes the way that the solver generates the summarized log that it displays at normal verbosity. Previously, the solver saved the full log from the start to the first backjump. Then it filtered the log using the conflict set from the node where the first backjump occurred, i.e., it removed all lines from the log that did not relate to variables in the conflict set. The solver also printed the final conflict set at the end of the log. This approach had several problems: 1. It was possible for the conflicts at the first backjump to be completely unrelated to the final conflict set (issue haskell#941). The conflicts in the summarized log could be irrelevant to the failure, for example, if they were introduced by only a single version of a dependency, which the solver could easily skip, and the real problem was a different dependency that was missing from the index. Even if the summarized log was relevant, it could differ from the final conflict set and be misleading. 2. Filtering the full log was error prone and could easily remove the wrong lines. It caused bugs mentioned in haskell#2853 and haskell#4154. 3. The conflict set at the first backjump contains the variables directly involved in the conflicts at that level and the variables that introduced them, but it doesn't contain the whole chain of variables starting with the user targets. When the log is filtered with that conflict set, it can be unclear why the solver needed to choose the conflicting packages in the first place. This commit creates the summarized log by rerunning the solver with a backjump limit of zero and using the full log. Using the full log avoids (2) and (3). However, it is also important to shorten the log by only showing choices that are relevant to conflicts. This commit uses different approaches for the two types of solver failure. No solution: This commit makes the solver prefer variables from the first run's final conflict set when choosing goals in the second run. This means that the log to the first backjump should be more relevant to the final failure, because it only mentions packages, flags, and stanzas from the final conflict set. (The solver shouldn't need to choose any packages that aren't in the conflict set, because, for every variable in the final conflict set, the final conflict set should also contain the variable that introduced that variable. The solver can follow that chain of variables in reverse order from the user target to the conflict.) Backjump limit reached: There is no final conflict set in this case, since the solver did not traverse the whole tree. This commit tries to create a final conflict set by rerunning the solver with a subtree of the original search tree that contains the path to the first backjump. Then it uses the final conflict set to generate a log message as above. Here is an example of the differences between the new and old logs, from haskell#4792, using GHC 8.2.1: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: contravariant (dependency of thorn) [__1] rejecting: contravariant-1.4, contravariant-1.3.3, contravariant-1.3.2, contravariant-1.3.1.1, contravariant-1.3.1, contravariant-1.3, contravariant-1.2.2.1, contravariant-1.2.2, contravariant-1.2.1, contravariant-1.2.0.1, contravariant-1.2, contravariant-1.1, contravariant-1.0 (conflict: thorn => contravariant<1) [__1] trying: contravariant-0.6.1.1 [__2] next goal: transformers (dependency of contravariant) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: contravariant => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn Differences: - The new summary has level numbers, like the full log. - The conflicts are different. The old log mentions thorn, base, profunctors, and transformers, and the new log mentions the four packages from the conflict set: thorn, contravariant, transformers, and base. - The new log starts with the solver choosing a user goal, thorn. The solver continues to display the conflicts at the first backjump when it reaches the backjump limit, i.e, it shows profunctors instead of contravariant. The goal order differs, though: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: profunctors (dependency of thorn) [__1] rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) [__1] trying: profunctors-4.4.1 [__2] next goal: transformers (dependency of profunctors) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). One downside of this change is that the solver may reach the backjump limit when generating the summarized log, if the backjump limit is small: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=1 Resolving dependencies... cabal: Backjump limit reached (currently 1, change with --max-backjumps or try to run with --reorder-goals). Failed to generate a summarized dependency solver log due to low backjump limit. Another downside is the performance impact of rerunning the solver. I timed solving for several packages, and there wasn't a significant difference in run time when the solver found a solution or failed after an exhaustive search. However, this branch was often significantly slower when the solver reached the backjump limit. The extra time was probably spent in the second run of the solver, where it had to traverse the tree to the first backjump. The worst case was acme-everything with GHC 7.10.3, where that step took 13 seconds. In other cases, it was less than a second. For example, 'cabal install --dry-run push-notify' took 5.62 seconds on master and 5.71 seconds on this branch, and 'cabal install --dry-run reactive-glut' took 3.77 seconds on master and 3.825 seconds on this branch (average of three trials).
grayjay
added a commit
to grayjay/cabal
that referenced
this pull request
Jan 9, 2018
…kell#4823). This commit changes the way that the solver generates the summarized log that it displays at normal verbosity. Previously, the solver saved the full log from the start to the first backjump. Then it filtered the log using the conflict set from the node where the first backjump occurred, i.e., it removed all lines from the log that did not relate to variables in the conflict set. The solver also printed the final conflict set at the end of the log. This approach had several problems: 1. It was possible for the conflicts at the first backjump to be unrelated to the final conflict set (issue haskell#941). The conflicts in the summarized log could be irrelevant to the failure, for example, if they were caused by only a single version of a dependency, which the solver could skip, and the real problem was that a different dependency was missing from the index. Even if the summarized log was relevant, showing two different explanations for the same failure could be confusing. 2. Filtering the full log was error prone and could remove the wrong lines. It caused bugs mentioned in haskell#2853 and haskell#4154. 3. The conflict set at the first backjump contains the variables directly involved in the conflicts at that level and the variables that introduced them, but it doesn't contain the whole chain of variables starting with the user targets. When the log is filtered with that conflict set, it can be unclear why the solver needed to choose the conflicting packages in the first place. This commit creates the summarized log by rerunning the solver with a backjump limit of zero and using the full log. Using the full log avoids (2) and (3). However, it is also important to shorten the log by only showing choices that are relevant to conflicts. This commit uses different approaches for the two types of solver failure. No solution: This commit makes the solver prefer variables from the first run's final conflict set when choosing goals in the second run. This means that the log to the first backjump is more likely to be relevant to the final failure, because it only mentions packages, flags, and stanzas from the final conflict set. Backjump limit reached: There is no final conflict set in this case, since the solver did not traverse the whole tree. This commit tries to create a final conflict set by rerunning the solver with a subtree of the original search tree that contains the path to the first backjump. Then it uses the final conflict set to generate a log message, as in the case where the solver found that there was no solution. Here is an example of the differences between the new and old logs, using the command from issue haskell#4792 and GHC 8.2.1: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: contravariant (dependency of thorn) [__1] rejecting: contravariant-1.4, contravariant-1.3.3, contravariant-1.3.2, contravariant-1.3.1.1, contravariant-1.3.1, contravariant-1.3, contravariant-1.2.2.1, contravariant-1.2.2, contravariant-1.2.1, contravariant-1.2.0.1, contravariant-1.2, contravariant-1.1, contravariant-1.0 (conflict: thorn => contravariant<1) [__1] trying: contravariant-0.6.1.1 [__2] next goal: transformers (dependency of contravariant) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: contravariant => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn Differences: - The new summary has level numbers, like the full log. - The conflicts are different. The old log mentions thorn, base, profunctors, and transformers, and the new log mentions the four packages from the conflict set: thorn, contravariant, transformers, and base. - The new log starts with the solver choosing a user goal, thorn. The solver continues to display the conflicts at the first backjump when it reaches the backjump limit, i.e, it shows profunctors instead of contravariant: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: profunctors (dependency of thorn) [__1] rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) [__1] trying: profunctors-4.4.1 [__2] next goal: transformers (dependency of profunctors) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). One downside of this change is that the solver may reach the backjump limit when generating the summarized log, if the backjump limit is very low: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=1 Resolving dependencies... cabal: Backjump limit reached (currently 1, change with --max-backjumps or try to run with --reorder-goals). Failed to generate a summarized dependency solver log due to low backjump limit. Another downside is the performance impact of rerunning the solver. It looks like there isn't a big change in run time when the solver finds a solution or fails after an exhaustive search. However, rerunning the solver to the first backjump after it reaches the backjump limit can take a significant amount of time. The worst case I could find was acme-everything with GHC 7.10.3, where that step took 13 seconds. I also ran hackage-benchmark on packages from Hackage to try to find packages where the run time changed by more than a few percent. I stopped it after all packages starting with "b" (That includes all uppercase packages). compiler: GHC 8.2.1 index state: 2018-01-04T21:05:55Z parameters: --min-run-time-percentage-difference-to-rerun=1 --pvalue=0.01 --trials=20 --print-skipped-packages Out of 2219 packages, 1064 were skipped because the run times in the first trial were within 1%, 1065 differed by more than 1% in the first trial but did not show a significant difference in run time in 20 trials, and 90 did show a significant difference in run time. Here are the package counts for different ranges of speedup, for those 90 packages: speedup (master avg. run time / branch avg. run time) package count [0.93, 0.94) 1 [0.94, 0.95) 0 [0.95, 0.96) 0 [0.96, 0.97) 1 [0.97, 0.98) 7 [0.98, 0.99) 29 [0.99, 1.00) 47 [1.00, 1.01) 3 [1.01, 1.02) 2 The package with the biggest change was bittorrent, which had a speedup of 0.936. It reached the backjump limit.
grayjay
added a commit
to grayjay/cabal
that referenced
this pull request
Jan 10, 2018
…kell#4823). This commit changes the way that the solver generates the summarized log that it displays at normal verbosity. Previously, the solver saved the full log from the start to the first backjump. Then it filtered the log using the conflict set from the node where the first backjump occurred, i.e., it removed all lines from the log that did not relate to variables in the conflict set. The solver also printed the final conflict set at the end of the log. This approach had several problems: 1. It was possible for the conflicts at the first backjump to be unrelated to the final conflict set (issue haskell#941). The conflicts in the summarized log could be irrelevant to the failure, for example, if they were caused by only a single version of a dependency, which the solver could skip, and the real problem was a different dependency that was missing from the index. Even if the summarized log was relevant, showing two different explanations for the same failure could be confusing. 2. Filtering the full log was error prone and could remove the wrong lines. It caused bugs mentioned in haskell#2853 and haskell#4154. 3. The conflict set at the first backjump contains the variables directly involved in the conflicts at that level and the variables that introduced them, but it doesn't contain the whole chain of variables starting with the user targets. When the log is filtered with that conflict set, it can be unclear why the solver needed to choose the conflicting packages in the first place. This commit creates the summarized log by rerunning the solver with a backjump limit of zero and using the full log. Using an unfiltered log avoids (2) and (3). However, it is also important to shorten the log by only showing choices that are relevant to conflicts. This commit uses different approaches for the two types of solver failures. No solution: This commit makes the solver prefer variables from the first run's final conflict set when choosing goals in the second run. This means that the log to the first backjump is more likely to be relevant to the final failure, because it only mentions packages, flags, and stanzas from the final conflict set. Backjump limit reached: There is no final conflict set in this case, since the solver did not traverse the whole tree. This commit tries to create a final conflict set by rerunning the solver with a subtree of the original search tree that contains the path to the first backjump. Then it uses the final conflict set from that run to generate a log message, as in the case where the solver found that there was no solution. Here is an example of the differences between the new and old logs, using the command from issue haskell#4792 and GHC 8.2.1: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: contravariant (dependency of thorn) [__1] rejecting: contravariant-1.4, contravariant-1.3.3, contravariant-1.3.2, contravariant-1.3.1.1, contravariant-1.3.1, contravariant-1.3, contravariant-1.2.2.1, contravariant-1.2.2, contravariant-1.2.1, contravariant-1.2.0.1, contravariant-1.2, contravariant-1.1, contravariant-1.0 (conflict: thorn => contravariant<1) [__1] trying: contravariant-0.6.1.1 [__2] next goal: transformers (dependency of contravariant) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: contravariant => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn Differences: - The new summary has level numbers, like the full log. - The conflicts are different. The old log mentions thorn, base, profunctors, and transformers, and the new log mentions the four packages from the conflict set: thorn, contravariant, transformers, and base. - The new log starts with the solver choosing a user goal, thorn. The solver continues to display the conflicts at the first backjump when it reaches the backjump limit, i.e, it shows profunctors instead of contravariant: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: profunctors (dependency of thorn) [__1] rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) [__1] trying: profunctors-4.4.1 [__2] next goal: transformers (dependency of profunctors) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). One downside of this change is that the solver may reach the backjump limit when generating the summarized log, if the backjump limit is very low: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=1 Resolving dependencies... cabal: Backjump limit reached (currently 1, change with --max-backjumps or try to run with --reorder-goals). Failed to generate a summarized dependency solver log due to low backjump limit. Another downside is the performance impact of rerunning the solver. It looks like there isn't a big change in run time when the solver finds a solution or fails after an exhaustive search. However, rerunning the solver to the first backjump after it reaches the backjump limit can take a significant amount of time. The worst case I could find was acme-everything with GHC 7.10.3, where that step took 13 seconds. The difference was normally small, though. I ran hackage-benchmark on packages from Hackage to try to find packages where the run time changed by more than a few percent. I stopped it after all packages starting with "b" (That includes all uppercase packages). compiler: GHC 8.2.1 index state: 2018-01-04T21:05:55Z parameters: --min-run-time-percentage-difference-to-rerun=1 --pvalue=0.01 --trials=20 --print-skipped-packages Out of 2219 packages, 1064 were skipped because the run times in the first trial were within 1%, 1065 differed by more than 1% in the first trial but did not show a significant difference in run time in 20 trials, and 90 did show a significant difference in run time. Here are the counts of packages for different ranges of speedup, for those 90 packages: speedup (master avg. run time / branch avg. run time) package count [0.93, 0.94) 1 [0.94, 0.95) 0 [0.95, 0.96) 0 [0.96, 0.97) 1 [0.97, 0.98) 7 [0.98, 0.99) 29 [0.99, 1.00) 47 [1.00, 1.01) 3 [1.01, 1.02) 2 The package with the biggest percentage change was bittorrent, which ran for 3.85 seconds on master and 4.12 seconds on this branch. It reached the backjump limit.
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…kell#4823). This commit changes the way that the solver generates the summarized log that it displays at normal verbosity. Previously, the solver saved the full log from the start to the first backjump. Then it filtered the log using the conflict set from the node where the first backjump occurred, i.e., it removed all lines from the log that did not relate to variables in the conflict set. The solver also printed the final conflict set at the end of the log. This approach had several problems: 1. It was possible for the conflicts at the first backjump to be unrelated to the final conflict set (issue haskell#941). The conflicts in the summarized log could be irrelevant to the failure, for example, if they were caused by only a single version of a dependency, which the solver could skip, and the real problem was a different dependency that was missing from the index. Even if the summarized log was relevant, showing two different explanations for the same failure could be confusing. 2. Filtering the full log was error prone and could remove the wrong lines. It caused bugs mentioned in haskell#2853 and haskell#4154. 3. The conflict set at the first backjump contains the variables directly involved in the conflicts at that level and the variables that introduced them, but it doesn't contain the whole chain of variables starting with the user targets (issue haskell#4792). When the log is filtered with that conflict set, it can be unclear why the solver needed to choose the conflicting packages in the first place. This commit creates the summarized log by rerunning the solver with a backjump limit of zero and using the full log. Using an unfiltered log avoids (2) and (3). However, it is also important to shorten the log by only showing choices that are relevant to conflicts. This commit uses different approaches for the two types of solver failures. No solution: This commit makes the solver prefer variables from the first run's final conflict set when choosing goals in the second run. This means that the log to the first backjump is more likely to be relevant to the final failure, because it only mentions packages, flags, and stanzas from the final conflict set. Backjump limit reached: There is no final conflict set in this case, since the solver did not traverse the whole tree. This commit tries to create a final conflict set by rerunning the solver with a subtree of the original search tree that contains the path to the first backjump. Then it uses the final conflict set from that run to generate a log message, as in the case where the solver found that there was no solution. Here is an example of the differences between the new and old logs, using the command from issue haskell#4792 and GHC 8.2.1: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: contravariant (dependency of thorn) [__1] rejecting: contravariant-1.4, contravariant-1.3.3, contravariant-1.3.2, contravariant-1.3.1.1, contravariant-1.3.1, contravariant-1.3, contravariant-1.2.2.1, contravariant-1.2.2, contravariant-1.2.1, contravariant-1.2.0.1, contravariant-1.2, contravariant-1.1, contravariant-1.0 (conflict: thorn => contravariant<1) [__1] trying: contravariant-0.6.1.1 [__2] next goal: transformers (dependency of contravariant) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: contravariant => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: transformers, contravariant, base, thorn Differences: - The new summary has level numbers, like the full log. - The conflicts are different. The old log mentions thorn, base, profunctors, and transformers, and the new log mentions the four packages from the conflict set: thorn, contravariant, transformers, and base. - The new log starts with the solver choosing a user goal, thorn. The solver continues to display the conflicts at the first backjump when it reaches the backjump limit, i.e, it shows profunctors instead of contravariant: Before: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: trying: base-4.10.0.0/installed-4.1... (dependency of thorn) next goal: profunctors (dependency of thorn) rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) trying: profunctors-4.4.1 next goal: transformers (dependency of profunctors) rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.3.0, transformers-0.4.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers => base>=2 && <4.9) rejecting: transformers-0.4.1.0, transformers-0.3.0.0, transformers-0.2.2.1 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.1.0, transformers-0.2.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.3) rejecting: transformers-0.1.4.0, transformers-0.1.3.0, transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0, transformers-0.0.0.0, transformers-0.5.3.1, transformers-0.5.3.0, transformers-0.5.0.2 (conflict: profunctors => transformers>=0.2 && <0.5) rejecting: transformers-0.4.0.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.8) rejecting: transformers-0.2.2.0 (conflict: base==4.10.0.0/installed-4.1..., transformers +/-applicativeinbase => base>=1.0 && <4.6) rejecting: transformers-0.1.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). After: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=10 Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: thorn-0.2 (user goal) [__1] next goal: profunctors (dependency of thorn) [__1] rejecting: profunctors-5.2.1, profunctors-5.2, profunctors-5.1.2, profunctors-5.1.1, profunctors-5.1, profunctors-5.0.1, profunctors-5.0.0.1, profunctors-5 (conflict: thorn => profunctors<5) [__1] trying: profunctors-4.4.1 [__2] next goal: transformers (dependency of profunctors) [__2] rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.5.0, transformers-0.5.4.0, transformers-0.5.2.0, transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0 (conflict: profunctors => transformers>=0.2 && <0.5) [__2] trying: transformers-0.4.3.0 [__3] next goal: base (dependency of thorn) [__3] rejecting: base-4.10.0.0/installed-4.1... (conflict: transformers => base>=2 && <4.9) [__3] rejecting: base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) Backjump limit reached (currently 10, change with --max-backjumps or try to run with --reorder-goals). One downside of this change is that the solver may reach the backjump limit when generating the summarized log, if the backjump limit is very low: $ cabal install --dry-run --index-state=2018-01-04T21:05:55Z thorn --max-backjumps=1 Resolving dependencies... cabal: Backjump limit reached (currently 1, change with --max-backjumps or try to run with --reorder-goals). Failed to generate a summarized dependency solver log due to low backjump limit. Another downside is the performance impact of rerunning the solver. It looks like there isn't a big change in run time when the solver finds a solution or fails after an exhaustive search. However, rerunning the solver to the first backjump after it reaches the backjump limit can take a significant amount of time. The worst case I could find was acme-everything with GHC 7.10.3, where that step took 13 seconds. The difference was normally small, though. I ran hackage-benchmark on packages from Hackage to try to find packages where the run time changed by more than a few percent. I stopped it after all packages starting with "b" (That includes all uppercase packages). compiler: GHC 8.2.1 index state: 2018-01-04T21:05:55Z parameters: --min-run-time-percentage-difference-to-rerun=1 --pvalue=0.01 --trials=20 --print-skipped-packages Out of 2219 packages, 1064 were skipped because the run times in the first trial were within 1%, 1065 differed by more than 1% in the first trial but did not show a significant difference in run time in 20 trials, and 90 did show a significant difference in run time. Here are the counts of packages for different ranges of speedup, for those 90 packages: speedup (master avg. run time / branch avg. run time) package count [0.93, 0.94) 1 [0.94, 0.95) 0 [0.95, 0.96) 0 [0.96, 0.97) 1 [0.97, 0.98) 7 [0.98, 0.99) 29 [0.99, 1.00) 47 [1.00, 1.01) 3 [1.01, 1.02) 2 The package with the biggest percentage change was bittorrent, which ran for 3.85 seconds on master and 4.12 seconds on this branch. It reached the backjump limit.
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This commit prevents cabal from filtering out messages about missing
packages when summarizing the solver trace.
In this example, it adds the line
fail (unknown package: either).This commit partially fixes issues #2179 and #2816 but doesn't remind the user to run
cabal update. If we mentionupdate, I think it should be a separate message, because this line can appear many times in the full trace.