Hi all, In semi-private I have been making very bold claims about the unsuitability of the devel2 as a build flavour of choice for the aspiring developer. In order to bolster my claim I set out to find out some statistics about 1. devel2 flavour 2. default+no_profiled_libs+omit_pragmas+assertions flavour The difference between the two is essentially that flavour (2) builds each module with optimisation but disables cross-module optimisation (in particular inlining) In short the difference between the two flavours is negligible from my testing apart from one larger difference when building larger packages. Full build + test: Near identical Testsuite run: Near identical Recompile: Near identical - (2) is slower Build Cabal: 167s vs 259s So if you want to build packages use flavour 2 but otherwise it seems to make little difference. Cheers, Matt
Interesting -- thanks for taking the time to do this.
Full build + test: Near identical Testsuite run: Near identical Recompile: Near identical - (2) is slower Build Cabal: 167s vs 259s
I assume from your statement that (2) is 167s and (1) is 259s? These results surprise me, in a few ways: - My understanding is that devel2 does not optimise (-O0) the stage-2 compiler. So I'm surprised that the testsuite runs in the same amount of time for both: I would expect (2) to be measurably faster. - And if the testsuite is the same for both, then I would expect "Build Cabal" to be the same for both: both measurements are looking at the performance of the stage-2 compiler. Yet the difference in time in "Build Cabal" is drastic. Why is this not echoed in the testsuite? (Maybe the testsuite overhead dwarfs the efficiency of the compiler itself?) - As we have discovered, devel2 behaves differently in the testsuite than your flavour (2). But your text suggests that the only difference is that devel2 is completely unoptimised... and yet the testsuite-behavior differences are not (I think) about performance. So there's some *other* difference. My key requirements in a build flavor are: A. assertions enabled B. quick recompilation C. < 3 spurious test case failures when running the testsuite locally I don't have any particular attachment to devel2, per se, other than that (with `make`, at least), it delivers A,B,C. My struggle with Hadrian is that devel2 no longer delivers C. If a different flavor provides A,B,C with Hadrian, I'm happy to give it a go. I'm a little worried about "(2) is slower" above, so my money is still with devel2, as delivering A,B,C better. Building packages is not one of my requirements. In any case, this is a good conversation to have, because it may yield an understanding that we should jettison or replace devel2. Thanks for starting it! Richard
So if you want to build packages use flavour 2 but otherwise it seems to make little difference.
Cheers,
Matt _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
participants (2)
-
Matthew Pickering -
Richard Eisenberg