Hi Oleg,
Thanks for the tutorial analysis and what looks like an excellent patch.
Regarding ffunctions with side effects, Stéphane recently helped me
get each of my ffunctions-with-state to have its own separate state
struct. If anyone needs that, let us know. We could post our simple
examples to this list or work them into the doc somewhere.
- Julius
On Sun, Oct 7, 2018 at 8:56 AM Stéphane Letz <l...@grame.fr> wrote:
>
> Thanks Oleg for the feedback, we’ll certainly have a look.
>
> Concerning « Foreign functions », they are supposed to be side effects free,
> see the "faust-quick-reference » :
>
> Foreign functions with input parameters are considered pure math functions.
> They are therefore considered free of side effects and called only when their
> parameters change (that is at the rate of the fastest parameter).
>
> Stéphane
>
> > Le 7 oct. 2018 à 16:01, Oleg Nesterov <o...@redhat.com> a écrit :
> >
> > test-case:
> >
> > // arbitrary kSamp signal
> > delay = ba.time : max(0) : min(10);
> > process = @(delay) <: _,_;
> >
> > result:
> >
> > iRec0[0] = ...;
> > output0[i] = FAUSTFLOAT(fVec0[std::min<int>(10, std::max<int>(0,
> > (iRec0[0] + -1)))]);
> > output1[i] = FAUSTFLOAT(fVec0[std::min<int>(10, std::max<int>(0,
> > (iRec0[0] + -1)))]);
> >
> > you can see that "delay" is evaluated twice. Not really a bug, but doesn't
> > look
> > good performance wise.
> >
> > Similarly,
> >
> > delay = ffunction(int func(),"","") : max(0) : min(10);
> > process = @(delay) <: _,_;
> >
> > results in
> >
> > output0[i] = FAUSTFLOAT(fVec0[std::min<int>(10, std::max<int>(0,
> > int(func())))]);
> > output1[i] = FAUSTFLOAT(fVec0[std::min<int>(10, std::max<int>(0,
> > int(func())))]);
> >
> > and this is worse in that func() may have side effects, it shouldn't be
> > called twice.
> >
> > This is because generateFixDelay() "ignores" getSharingCount(sig) so for
> > example
> >
> > process = mem <: _,_;
> >
> > doesn't imply generateVariableStore() and this is fine. However this also
> > means
> > that "delay" will be evaluated every time, its getSharingCount() == 1
> > unless it
> > has another user; sharingAnnotation(sig) will not look at getSubSignals(ig)
> > if
> > getSharingCount(sig) is already non zero.
> >
> > With the "patch" below
> >
> > delay = ffunction(int func(),"","") : max(0) : min(10);
> > process = @(delay) <: _,_;
> >
> > compiles to
> >
> > int iTemp0 = std::min<int>(10, std::max<int>(0, int(func())));
> > output0[i] = FAUSTFLOAT(fVec0[iTemp0]);
> > output1[i] = FAUSTFLOAT(fVec0[iTemp0]);
> >
> > and this is what I think faust should actually do.
> >
> > Oleg.
> >
> >
> > --- a/compiler/generator/instructions_compiler.cpp
> > +++ b/compiler/generator/instructions_compiler.cpp
> > @@ -697,6 +697,9 @@ ValueInst* InstructionsCompiler::generateFixDelay(Tree
> > sig, Tree exp, Tree delay
> > }
> > }
> >
> > +if (getSharingCount(delay)==1 && getSharingCount(sig)>1)
> > + setSharingCount(delay, 2);
> > +
> > if (mxd == 0) {
> > return InstBuilder::genLoadStackVar(vname);
> > } else if (mxd < gGlobal->gMaxCopyDelay) {
> >
>
>
>
> _______________________________________________
> Faudiostream-devel mailing list
> Faudiostream-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/faudiostream-devel
--
Julius O. Smith III <j...@ccrma.stanford.edu>
Professor of Music and, by courtesy, Electrical Engineering
CCRMA, Stanford University
http://ccrma.stanford.edu/~jos/
_______________________________________________
Faudiostream-devel mailing list
Faudiostream-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/faudiostream-devel
