Would it be worth adding some info from the commit message to the comment with type MPZ#? In particular, the little table you give in the commit message is helpful, but someone looking at the code won't see it. This is subtle stuff. Simon | -----Original Message----- | From: ghc-commits [mailto:ghc-commits-bounces@haskell.org] On Behalf Of | git@git.haskell.org | Sent: 12 January 2014 23:37 | To: ghc-commits@haskell.org | Subject: [commit: packages/integer-gmp] wip/T8647: Allocate initial 1- | limb mpz_t on the Stack and introduce MPZ# type (20d7bfd) | | Repository : ssh://git@git.haskell.org/integer-gmp | | On branch : wip/T8647 | Link : | http://ghc.haskell.org/trac/ghc/changeset/20d7bfdd29917f5a8b8937fba9b724 | f7e71cd8dd/integer-gmp | | >--------------------------------------------------------------- | | commit 20d7bfdd29917f5a8b8937fba9b724f7e71cd8dd | Author: Herbert Valerio Riedel | Date: Thu Jan 9 00:19:31 2014 +0100 | | Allocate initial 1-limb mpz_t on the Stack and introduce MPZ# type | | We now allocate a 1-limb mpz_t on the stack instead of doing a more | expensive heap-allocation (especially if the heap-allocated copy | becomes | garbage right away); this addresses #8647. | | In order to delay heap allocations of 1-limb `ByteArray#`s instead | of | the previous `(# Int#, ByteArray# #)` pair, a 3-tuple | `(# Int#, ByteArray#, Word# #)` is returned now. This tuple is given | the | type-synonym `MPZ#`. | | This 3-tuple representation uses either the 1st and the 2nd element, | or | the 1st and the 3rd element to represent the limb(s) (NB: undefined | `ByteArray#` elements must not be accessed as they don't point to a | proper `ByteArray#`, see also `DUMMY_BYTE_ARR`); more specifically, | the | following encoding is used (where `⊥` means undefined/unused): | | - (# 0#, ⊥, 0## #) -> value = 0 | - (# 1#, ⊥, w #) -> value = w | - (# -1#, ⊥, w #) -> value = -w | - (# s#, d, 0## #) -> value = J# s d | | The `mpzToInteger` helper takes care of converting `MPZ#` into an | `Integer`, and allocating a 1-limb `ByteArray#` in case the | value (`w`/`-w`) doesn't fit the `S# Int#` representation). | | The following nofib benchmarks benefit from this optimization: | | Program Size Allocs Runtime Elapsed TotalMem | ------------------------------------------------------------------ | bernouilli +0.2% -5.2% 0.12 0.12 +0.0% | gamteb +0.2% -1.7% 0.03 0.03 +0.0% | kahan +0.3% -13.2% 0.17 0.17 +0.0% | mandel +0.2% -24.6% 0.04 0.04 +0.0% | power +0.2% -2.6% -2.0% -2.0% -8.3% | primetest +0.1% -17.3% 0.06 0.06 +0.0% | rsa +0.2% -18.5% 0.02 0.02 +0.0% | scs +0.1% -2.9% -0.1% -0.1% +0.0% | sphere +0.3% -0.8% 0.03 0.03 +0.0% | symalg +0.2% -3.1% 0.01 0.01 +0.0% | ------------------------------------------------------------------ | Min +0.1% -24.6% -4.6% -4.6% -8.3% | Max +0.3% +0.0% +5.9% +5.9% +4.5% | Geometric Mean +0.2% -1.0% +0.2% +0.2% -0.0% | | Signed-off-by: Herbert Valerio Riedel | | | >--------------------------------------------------------------- | | 20d7bfdd29917f5a8b8937fba9b724f7e71cd8dd | GHC/Integer/GMP/Prim.hs | 88 ++++++++++++------- | GHC/Integer/Type.lhs | 160 +++++++++++++++------------------ | cbits/gmp-wrappers.cmm | 224 +++++++++++++++++++++++++++++++++------- | ------- | 3 files changed, 285 insertions(+), 187 deletions(-) | | Diff suppressed because of size. To see it, use: | | git diff-tree --root --patch-with-stat --no-color --find-copies- | harder --ignore-space-at-eol --cc | 20d7bfdd29917f5a8b8937fba9b724f7e71cd8dd | _______________________________________________ | ghc-commits mailing list | ghc-commits@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-commits