#3489: Adding some gmp bindings to integer-gmp (copied from the cvs-ghc list)
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Reporter: pumpkin | Owner:
Type: proposal | Status: new
Priority: normal | Component: Compiler
Version: 6.11 | Severity: minor
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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This is my first patch for GHC, so I apologize in advance if I do
something wrong! I've actually attached three patches for
libraries/base, libraries/integer-gmp, and libraries/integer-simple, but
because there is no change to any exposed API and only a couple of extra
functions added to GHC.Integer, I'm sending it here instead of to
libraries at haskell.org.
Basically, I added cmm bindings to mpz_powm(_ui), mpz_tstbit, and
mpz_sizeinbase. The modular exponentiation function is significantly
faster than anything I could find in pure haskell, and the bit testing is
way more efficient than the default Data.Bits implementation involving a
potentially massive left shift (in fact, might that be better phrased as a
right shift of the tested value?). The sizeinbase function (essentially an
integer logarithm, unfortunately with the base restricted to a maximum of
62) also looked handy so I added it while I was there (at Bertram
Felgenhauer's suggestion).
So these patches amount to:
* A one-line change to Data.Bits in base, adding our specialized testBit
function.
* Some cmm code additions in integer-gmp, plus the Haskell glue to make
them usable from outside.
* A very simplistic implementation of testBitInteger for integer-simple,
so that the one-line change to Data.Bits doesn't fail
when building with integer-simple.
I've tested the code and it appears to be correct, and have validated it
with both integer-simple and -gmp, in both cases encountering two
unexpected ghci test failures (in OS X): ghci028 and 2816. Manuel
Chakravarty said these were normal and that he'd experienced the build
failures under OS X too, so I didn't look into them any more deeply.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3489>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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