| Would it be possible for the compiler to say something like: You are
| applying level 2 optimization but some dependencies where compiled without
| optimization enabled. To get full optimization, consider recompiling x,y,z
| with -O2 - at least this would give us a fighting chance to 'fix'
I suspect that if all modules are compiled -O0, then you recompile one
module with -O2, high up in the dependency graph (i.e. it depends on
many lower-level modules), plus all things that in turn depend on it
(--make), you will not get the good performance you expect. None of the
lower-level
| I'd be interested in any progress here -- we noticed issues with
| optimisations in the stream fusion package across module boundaries
| that we never tracked down. If there's some key things not firing,
| that would be good to know.
|
| I suspect that if all modules are compiled -O0, then
On Thu, Mar 20, 2008 at 09:47:28AM +0100, Bernd Brassel wrote:
compiled things with -O2 AND -prof -auto-all no profile would be
written.
This should work, for the reasons that you give. Did you use options
like +RTS -p when running the program? If so, please give us an example
to reproduce
| I'd be interested in any progress here -- we noticed issues with
| optimisations in the stream fusion package across module boundaries
| that we never tracked down. If there's some key things not firing,
| that would be good to know.
|
| I suspect that if all modules are compiled -O0,
bbr:
I suspect that if all modules are compiled -O0, then you recompile one
module with -O2, high up in the dependency graph (i.e. it depends on
many lower-level modules), plus all things that in turn depend on it
(--make), you will not get the good performance you expect. None of the
Don Stewart wrote:
You almost always want to profile with full optimisations on.
Otherwise its not even close to measuring the kind of code you're
actually running.
Ian Lynagh wrote:
This should work, for the reasons that you give. Did you use options
like +RTS -p when running the program?
Hi all,
I have noticed that there is a great difference between optimizing
modules separately and all at once, e.g., with -fforce-recomp. I have
had examples factors up to 15 in run time (and even different behavior
in context with unsafePerformIO).
Is there any option that makes ghc write out
| I have noticed that there is a great difference between optimizing
| modules separately and all at once, e.g., with -fforce-recomp. I have
| had examples factors up to 15 in run time (and even different behavior
| in context with unsafePerformIO).
GHC does a lot of cross-module inlining
Simon Peyton-Jones wrote:
GHC does a lot of cross-module inlining already, and *does* write stuff into
interface files, provided you use -O.
I used -O4. Is that the bad thing?
I'm always interested in performance differences of a factor of 15 though!
Can you supply an example (as small
bbr:
Simon Peyton-Jones wrote:
GHC does a lot of cross-module inlining already, and *does* write stuff
into interface files, provided you use -O.
I used -O4. Is that the bad thing?
There's nothing about -O2
However, I think that's ok -- it clamps -ON | N2 to -O2
I'm always
I'd be interested in any progress here -- we noticed issues with
optimisations in the stream fusion package across module boundaries
that we never tracked down. If there's some key things not firing,
that would be good to know.
I suspect that if all modules are compiled -O0, then you
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