Phil Carmody on Thu, 06 Nov 2003 21:52:41 +0100 |
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Re: Experimenting with the Alpha build. |
--- Karim BELABAS <Karim.Belabas@math.u-psud.fr> wrote: > On Thu, 6 Nov 2003, Phil Carmody wrote: > > I was wondering if -ffast-math would do to Pari/GP/GMP on the alpha. > > The speed-ups weren't significant on the whole (I should have tried > > -mno-ieee too perhaps) > > This is expected: there's almost no floating point code in PARI (everything > is emulated using 'unsigned long' arithmetic). Might be considered a > shortcoming. > > There are lots of variables of type 'double', but they are used in parts of > the code which is negligible timewise. And never where stability / accuracy > is important. I.e --fast-math should be a no-op with respect to performances > or results. I also recompiled GMP with -ffast-math too for the test. In theory GMP might perform some FP maths (FFT multiplication? or is it NTT?). I wasn't expecting massive changes, I just fancied experimenting. The only ones that had an improvement more than the likely noise floor were: * Testing analyz for gp-sta..TIME=445 for gp-dyn..TIME=399 * Testing number for gp-sta..TIME=226 for gp-dyn..TIME=231 vs. the "slow" old * Testing analyz for gp-sta..TIME=463 for gp-dyn..TIME=411 * Testing number for gp-sta..TIME=242 for gp-dyn..TIME=243 analyz is a bit weird - I was expecting -dyn to by slower than -sta across the board. > I have just dumped this part of the result in CVS. Same goes for bnfinit, and > a few other diagnostics which have cluttered outputs for no good reason > ( bnfisprincipal / bnrisprincipal ). > > The minor backward incompatibility should not pose a problem, since I do not > see any situation where this component would need to be accessed. Heheh, sorry for diverting you onto trivialities. Experimentation is in my nature, alas... Phil ===== When inserting a CD, hold down shift to stop the AutoRun feature In the Device Manager, disable the SbcpHid device. http://www.cs.princeton.edu/~jhalderm/cd3/ __________________________________ Do you Yahoo!? Protect your identity with Yahoo! Mail AddressGuard http://antispam.yahoo.com/whatsnewfree