Revert union, difference, etc. complexity changes #958
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As discussed in haskell#870, the complexities for union, difference, etc. on Set and Map were changed in haskell#830 to fix some partiality in the expressions, but along the way new partiality was introduced, and useful special cases like m = 1 get incorrect complexity values from the new formulas. The original formula was as stated in the original paper: https://dl.acm.org/doi/10.1145/322123.322127 and this holds for 0 < m <= n, which seems sufficient to me. (The m=0 case is excluded, but for m=0 nothing needs to be done anyway. This contrary to the m=1 case, in which useful work with very specific complexity (namely, O(log(n))) needs to be done.) This commit reverts all occurrences of the modified complexity formula back to the original one.
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For now, we'll go with it. I would rather have something more complete. |
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As discussed in #870, the complexities for union, difference, etc. on Set and Map were changed in #830 to fix some partiality in the expressions, but along the way new partiality was introduced, and useful special cases like m = 1 get incorrect complexity values from the new formulas.
The original formula was as stated in the original paper:
https://dl.acm.org/doi/10.1145/322123.322127
and this holds for 0 < m <= n, which seems sufficient to me. (The m=0 case is excluded, but for m=0 nothing needs to be done anyway. This contrary to the m=1 case, in which useful work with very specific complexity (namely, O(log(n))) needs to be done.)
This commit reverts all occurrences of the modified complexity formula back to the original one.
NOTE: I have not checked that all functions for which I changed the complexity specification are indeed instances of the algorithms in the original paper. However, due to the quite specific complexity formula that is unlikely to occur anywhere else, I think this is correct anyway.