Add link{L,R} for Set and Map #1141
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linkL restores balance when the left tree is too heavy for the right tree, but unlike link it skips checking the other way around. linkR handles the opposite. linkL and linkR are used where we know the direction in which we need to rebalance. linkL and linkR delegate to linkL_ and linkR_, which do the actual work. link also delegates to linkL_ and linkR_, since the direction does not change when linking two trees. This single-direction linking algorithm can be seen in Figure 4 of "Parallel Ordered Sets Using Join". Similarly, link2/merge delegates to link2L_,link2_R/mergeL_,mergeR_. Benchmarks show a decrease in time and allocations, especially in set-set operations like union. Inspection of the Core of the previous link implementation revealed that it reboxes trees in some cases, which explains the decrease in allocations.
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Benchmarks on GHC 9.12.2: Set-setMap-map |
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linkL restores balance when the left tree is too heavy for the right tree, but unlike link it skips checking the other way around. linkR handles the opposite. linkL and linkR are used where we know the direction in which we need to rebalance.
linkL and linkR delegate to linkL_ and linkR_, which do the actual work. link also delegates to linkL_ and linkR_, since the direction does not change when linking two trees. This single-direction linking algorithm can be seen in Figure 4 of "Parallel Ordered Sets Using Join". Similarly, link2/merge delegates to link2L_,link2_R/mergeL_,mergeR_.
Benchmarks show a decrease in time and allocations, especially in set-set operations like union. Inspection of the Core of the previous link implementation revealed that it reboxes trees in some cases, which explains the decrease in allocations.
Closes #307.