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tests: extend the fmt=4 oracle to the fused gate+up kernel (#298)

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@woolcoxm's matmul_i4_grouped_pair reads x once instead of twice for the
gate+up pair. Verified here against his branch (86e91b1 merged onto dev):
correct to ~2e-8 relative vs the double reference, and BIT-EXACT against two
separate matmul_i4_grouped calls on aligned shapes -- which is the shape the
real g64 checkpoints have (I = 2048 / 6144, gs = 64). His kernel is good.

Guarded behind COLI_HAVE_GROUPED_PAIR since the function only exists on that
branch; add -DCOLI_HAVE_GROUPED_PAIR to the test's Makefile rule when #298
lands and the pair cases activate.

The checks are deliberately asymmetric, and the reason is worth recording.
Bit-exactness is asserted ONLY when I % gs == 0: there every group is covered
by the AVX2 body, whose accumulation order matches the unfused kernel, so any
difference is a real bug. With a partial last group the tail falls to scalar
code and the compiler may contract/reassociate the fused body differently,
producing ~1e-7 differences -- rounding, not logic. My first version demanded
bit-exactness everywhere and duly "found" a bug in his kernel that did not
exist; the tell was that only `up` differed and never `gate`, which is FP luck
rather than a code path. Correctness is checked everywhere against the double
reference; identity only where identity is actually implied.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
JustVugg
2026-07-16 17:27:06 +02:00
parent 2a5961a01b
commit ac7103fe9c
1 changed files with 75 additions and 0 deletions
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c/tests/test_i4_grouped.c
+75
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@@ -93,6 +93,72 @@ static int check(const char *name, int S, int I, int O, int gs, int fill_edges){
return 0;
}
/* matmul_i4_grouped_pair (fused gate+up, #298) reads x once instead of twice.
* Checked two ways, because "identical" is only true where it can be:
*
* - Correctness, always: both outputs must match the double reference within
* the same magnitude-relative epsilon as the unfused kernel.
* - Bit-exactness, only when I % gs == 0: then every group is covered by the
* AVX2 body, whose accumulation order is identical to the unfused kernel, so
* the results agree to the last bit. This is the shape the real g64
* checkpoints have (I = 2048 / 6144, gs = 64), i.e. the production path.
*
* With a PARTIAL last group the group tail falls to scalar code, and the
* compiler is free to contract/reassociate the fused body differently from the
* single-matrix one. The results then differ by ~1e-7 -- rounding, not logic
* (which of gate/up "differs" is arbitrary, the tell that it is FP luck).
* Demanding bit-exactness there would report a compiler artifact as a bug. */
#ifdef COLI_HAVE_GROUPED_PAIR
static int check_pair(const char *name, int S, int I, int O, int gs){
int rb=(I+1)/2, ng=(I+gs-1)/gs;
uint8_t *qg=malloc((size_t)O*rb), *qu=malloc((size_t)O*rb);
float *sg=malloc((size_t)O*ng*sizeof(float)), *su=malloc((size_t)O*ng*sizeof(float));
float *x=malloc((size_t)S*I*sizeof(float));
float *yg=malloc((size_t)S*O*sizeof(float)), *yu=malloc((size_t)S*O*sizeof(float));
float *rg=malloc((size_t)S*O*sizeof(float)), *ru=malloc((size_t)S*O*sizeof(float));
double *dg=malloc((size_t)S*O*sizeof(double)), *du=malloc((size_t)S*O*sizeof(double));
double *mg=malloc((size_t)S*O*sizeof(double)), *mu=malloc((size_t)S*O*sizeof(double));
if(!qg||!qu||!sg||!su||!x||!yg||!yu||!rg||!ru||!dg||!du||!mg||!mu){ fprintf(stderr,"%s: OOM\n",name); return 1; }
for(size_t i=0;i<(size_t)O*rb;i++){ qg[i]=(uint8_t)(xr()&0xFF); qu[i]=(uint8_t)(xr()&0xFF); }
for(int i=0;i<O*ng;i++){ sg[i]=frand(); su[i]=frand(); }
for(int i=0;i<S*I;i++) x[i]=frand();
matmul_i4_grouped_pair(yg,yu,x,qg,sg,qu,su,S,I,O,gs);
matmul_i4_grouped(rg,x,qg,sg,S,I,O,gs);
matmul_i4_grouped(ru,x,qu,su,S,I,O,gs);
ref_grouped(dg,mg,x,qg,sg,S,I,O,gs);
ref_grouped(du,mu,x,qu,su,S,I,O,gs);
int bad=0, exact=1; double worst=0;
for(int i=0;i<S*O;i++){
double eg = mg[i]>1e-30 ? fabs((double)yg[i]-dg[i])/mg[i] : fabs((double)yg[i]-dg[i]);
double eu = mu[i]>1e-30 ? fabs((double)yu[i]-du[i])/mu[i] : fabs((double)yu[i]-du[i]);
if(eg>worst) worst=eg;
if(eu>worst) worst=eu;
if(eg>1e-6||eu>1e-6){
if(bad<3) fprintf(stderr,"%s: [%d] gate %.9g/%.9g up %.9g/%.9g (rel %.3g/%.3g)\n",
name,i,(double)yg[i],dg[i],(double)yu[i],du[i],eg,eu);
bad++;
}
if(yg[i]!=rg[i]||yu[i]!=ru[i]) exact=0;
}
/* Aligned shapes run entirely through the AVX2 body: same order as unfused,
* so bit-exactness is a real invariant there and worth asserting. */
if(I%gs==0 && !exact){
fprintf(stderr,"%s: FAIL fused != unfused bitwise on an ALIGNED shape "
"(no scalar tail runs here; the orders must match)\n",name);
bad++;
}
free(qg);free(qu);free(sg);free(su);free(x);free(yg);free(yu);free(rg);free(ru);
free(dg);free(du);free(mg);free(mu);
if(bad){ fprintf(stderr,"%s: FAIL (%d mismatched)\n",name,bad); return 1; }
printf(" %-42s ok (S=%d I=%d O=%d gs=%d, worst rel %.2g%s)\n",name,S,I,O,gs,worst,
I%gs==0?", bit-exact vs unfused":"");
return 0;
}
#endif
int main(void){
int fail=0;
printf("test_i4_grouped: matmul_i4_grouped vs plain-C dequant reference\n");
@@ -120,6 +186,15 @@ int main(void){
/* batch: S>1 exercises the per-s inner loop against a shared scale row */
fail|=check("gs=64, batch S=8", 8, 320, 6, 64, 0);
#ifdef COLI_HAVE_GROUPED_PAIR
printf("test_i4_grouped: matmul_i4_grouped_pair (fused gate+up) vs two separate calls\n");
fail|=check_pair("pair: gs=64, I multiple of gs", 2, 512, 8, 64);
fail|=check_pair("pair: gs=64, partial last group",2, 200, 4, 64);
fail|=check_pair("pair: gs=64, odd I (I=201)", 2, 201, 4, 64);
fail|=check_pair("pair: gs=64, decode S=1", 1, 320, 6, 64);
fail|=check_pair("pair: gs=128, I=512", 2, 512, 4, 128);
#endif
if(fail){ printf("test_i4_grouped: FAIL\n"); return 1; }
printf("test_i4_grouped: ok\n");
return 0;