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) {
>
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