This atan2 optimisation is easy, done in
https://github.com/grame-cncm/faust/commit/26537a42f0fe55c7d471cdbb968755bec92c1707
Stéphane
> Le 29 avr. 2023 à 18:41, Oleg Nesterov <o...@redhat.com> a écrit :
>
> Stephane, Yann,
>
> Can I suggest another feature? The patch is not for inclusion yet,
> but I'd like to discuss the idea / implementation.
>
> It adds the new keyword `meta` which returns the environment with
> 2 primitives (so far):
>
> 1. serial(sig) - returns sig->serial()
> 2. order(sig) - getSigOrder(sig)
>
> Note that they compute the returned value at compile time.
>
> Why the environment? Because this way it is very easy to add more
> primitives (e.g. typeof(sig) which returns kBool / kInt / kReal)
> using a single keyword.
>
> Why do we want this feature? Well, I certainly do ;) but I do not
> have a simple and convincing example.
>
> -------------------------------------------------------------------------------
> But let me provide a basic example even if it is not convincing.
> Consider:
>
> process(x,y) = atan2(x,x), atan2(x,y);
>
> it compiles to
>
> float fTemp0 = float(input0[i0]);
> output0[i0] = FAUSTFLOAT(std::atan2(fTemp0, fTemp0));
> output1[i0] = FAUSTFLOAT(std::atan2(fTemp0, float(input1[i0])));
>
> note that atan2(fTemp0, fTemp0) == %pi/4 (lets ignore the fTemp0 == 0
> case for the sake of simplicity), so this code is suboptimal.
>
> Let's try to improve this code:
>
> my_atan2(a,b) = select2(a == b, atan2(a,b), ma.PI/4);
> process(x,y) = my_atan2(x,x), my_atan2(x,y);
>
> result:
>
> float fTemp0 = float(input0[i0]);
> output0[i0] = FAUSTFLOAT(((fTemp0 == fTemp0) ? 0.7853982f :
> std::atan2(fTemp0, fTemp0)));
> float fTemp1 = float(input1[i0]);
> output1[i0] = FAUSTFLOAT(((fTemp0 == fTemp1) ? 0.7853982f :
> std::atan2(fTemp0, fTemp1)));
>
> doesn't look very good although the compiler will optimize out the 1st
> `fTemp0 == fTemp0` check.
>
> Now let's use meta.serial:
>
> same_signal(a,b) = meta.serial(a) == meta.serial(b);
>
> my_atan2(a,b) = select2(same_signal(a,b), atan2(a,b), ma.PI/4);
> process(x,y) = my_atan2(x,x), my_atan2(x,y);
>
> result:
>
> output0[i0] = FAUSTFLOAT(0.7853982f);
> output1[i0] = FAUSTFLOAT(std::atan2(float(input0[i0]),
> float(input1[i0])));
>
> Oleg.
> ---
> compiler/extended/metaprim.hh | 94 +++++++++++++++++++++++++++++++++++
> compiler/global.cpp | 3 ++
> compiler/global.hh | 2 +
> compiler/parser/faustlexer.l | 2 +
> compiler/parser/faustparser.y | 3 ++
> 5 files changed, 104 insertions(+)
> create mode 100644 compiler/extended/metaprim.hh
>
> diff --git a/compiler/extended/metaprim.hh b/compiler/extended/metaprim.hh
> new file mode 100644
> index 000000000..20cc5982e
> --- /dev/null
> +++ b/compiler/extended/metaprim.hh
> @@ -0,0 +1,94 @@
> +/************************************************************************
> + ************************************************************************
> + FAUST compiler
> + Copyright (C) 2003-2018 GRAME, Centre National de Creation Musicale
> + ---------------------------------------------------------------------
> + This program is free software; you can redistribute it and/or modify
> + it under the terms of the GNU Lesser General Public License as published
> by
> + the Free Software Foundation; either version 2.1 of the License, or
> + (at your option) any later version.
> +
> + This program is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + GNU Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public License
> + along with this program; if not, write to the Free Software
> + Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> + ************************************************************************
> + ************************************************************************/
> +
> +#include "xtended.hh"
> +#include "simplify.hh"
> +#include "sigorderrules.hh"
> +
> +class MetaPrim : public xtended {
> + private:
> + int fOp;
> + public:
> + MetaPrim(int op, const char *name) : xtended(name), fOp(op) {}
> +
> + virtual unsigned int arity() { return 1; }
> +
> + virtual bool needCache() { return true; }
> +
> + virtual int infereSigOrder(const std::vector<int>& args) { return 0; }
> +
> + virtual Tree computeSigOutput(const std::vector<Tree>& args)
> + {
> + Tree sig = simplify(args[0]);
> + int ret = -1;
> +
> + switch (fOp) {
> + case 0:
> + ret = sig->serial();
> + break;
> + case 1:
> + ret = getSigOrder(sig);
> + break;
> + default:
> + faustassert(false);
> + }
> +
> + return tree(ret);
> + }
> +
> + virtual ::Type infereSigType(ConstTypes args)
> + {
> + faustassert(false); return 0;
> + }
> +
> + virtual ValueInst* generateCode(CodeContainer* container, Values& args,
> ::Type result, ConstTypes types)
> + {
> + faustassert(false); return 0;
> + }
> +
> + virtual std::string generateCode(Klass* klass, const
> std::vector<std::string>& args, ConstTypes types)
> + {
> + faustassert(false); return 0;
> + }
> +
> + virtual std::string generateLateq(Lateq* lateq, const
> std::vector<std::string>& args, ConstTypes types)
> + {
> + return "TODO";
> + }
> +};
> +
> +static Tree add_meta_def(Tree defs, int op, const char *d_n)
> +{
> + Tree id = boxIdent(d_n);
> + std::string x_n = std::string("meta_") + d_n;
> + MetaPrim *meta = new MetaPrim(op, x_n.c_str());
> + return cons(cons(id, meta->box()), defs);
> +}
> +
> +static Tree mkMetaEnv()
> +{
> + Tree defs = gGlobal->nil;
> +
> + defs = add_meta_def(defs, 0, "serial");
> + defs = add_meta_def(defs, 1, "order");
> +
> + return boxWithLocalDef(boxEnvironment(), defs);
> +}
> diff --git a/compiler/global.cpp b/compiler/global.cpp
> index 29af5eb9d..6636eac92 100644
> --- a/compiler/global.cpp
> +++ b/compiler/global.cpp
> @@ -48,6 +48,7 @@
> #include "sourcereader.hh"
> #include "sqrtprim.hh"
> #include "tanprim.hh"
> +#include "metaprim.hh"
> #include "tree.hh"
> #include "occur.hh"
> #include "enrobage.hh"
> @@ -592,6 +593,8 @@ void global::init()
> // Predefined nil tree
> nil = tree(NIL);
>
> + gMetaEnv = mkMetaEnv();
> +
> PROCESS = symbol("process");
>
> BOXTYPEPROP = tree(symbol("boxTypeProp"));
> diff --git a/compiler/global.hh b/compiler/global.hh
> index e8ced28c8..dbb001e7c 100644
> --- a/compiler/global.hh
> +++ b/compiler/global.hh
> @@ -322,6 +322,8 @@ struct global {
> xtended* gAtan2Prim;
> xtended* gAsinPrim;
>
> + Tree gMetaEnv;
> +
> // Signals
> Sym BOXIDENT;
> Sym BOXCUT;
> diff --git a/compiler/parser/faustlexer.l b/compiler/parser/faustlexer.l
> index c92210cb5..c9342848f 100644
> --- a/compiler/parser/faustlexer.l
> +++ b/compiler/parser/faustlexer.l
> @@ -198,6 +198,8 @@ NSID {ID}("::"{ID})*
> "sum" return ISUM;
> "prod" return IPROD;
>
> +"meta" return META;
> +
> "inputs" return INPUTS;
> "outputs" return OUTPUTS;
>
> diff --git a/compiler/parser/faustparser.y b/compiler/parser/faustparser.y
> index 0f29d3403..5c9d49379 100644
> --- a/compiler/parser/faustparser.y
> +++ b/compiler/parser/faustparser.y
> @@ -217,6 +217,8 @@ inline Tree unquote(char* str)
> %token ISUM
> %token IPROD
>
> +%token META
> +
> %token INPUTS
> %token OUTPUTS
>
> @@ -587,6 +589,7 @@ primitive : INT { $$ =
> boxInt(str2int(FAUSTtext)
> | ffunction { $$ = boxFFun($1); }
> | fconst { $$ = $1; }
> | fvariable { $$ = $1; }
> + | META { $$ = gGlobal->gMetaEnv; }
> | COMPONENT LPAR uqstring RPAR { $$ = boxComponent($3); }
> | LIBRARY LPAR uqstring RPAR { $$ = boxLibrary($3); }
> | ENVIRONMENT LBRAQ stmtlist RBRAQ { $$ =
> boxWithLocalDef(boxEnvironment(),formatDefinitions($3)); }
> --
> 2.39.2
>
>
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