* Andrew Coppin <[EMAIL PROTECTED]> [070608 02:45]: > Bayley, Alistair wrote: > > [[1]mailto:[EMAIL PROTECTED] On Behalf Of Andrew Coppin > > Donald Bruce Stewart wrote: > > Some things to remember using Doubles: > > * {-# OPTIONS -fexcess-precision #-} > * -fvia-C > * -fbang-patterns > * -optc-O2 -optc-mfpmath=sse -optc-msse2 > * -optc-march=pentium4 > > 1. What do all those things do? > 2. Is the effect actually that large? > > Large? Depends what you mean by large, but adding a few flags to get > just a 10-20% speedup isn't to be ignored: > > Sure - if it really is 10-20%. (And not, say, 0.001 - 0.002%.)
A single data point for all of this, I have a program that calculates: P^1_i = S_i/sum_k S_k P^m_i = sum_{k!=i} P^1_k*P^m-1_i(S_~k) Here's timings for the different options: options run time compile time none 46.401 3.136 -O 5.033 4.906 -O2 4.967 6.755 -O2 -fexcess-precision 3.710 6.396 all listed options 3.602 6.344 Results with -fexcess-precision are very insignificantly different (1.0 e-7). _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe