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ggml-quants : better and faster make_qkxs_quants

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Francis Couture-Harpin
2025-02-21 15:05:03 -05:00
parent dd6b8408c9
commit d0060fc498
1 changed files with 123 additions and 70 deletions
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165
ggml/src/ggml-quants.c
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@@ -660,58 +660,119 @@ static inline int compare_fractions_desc(const void * a, const void * b) {
// exhaustive search with cumulative sums
// Need Faux to have room for n*(max(abs(nmin), abs(nmax))) fractions
static float make_qkxs_quants(int n, int nmin, int nmax, const float * restrict x, const float * restrict weights, int8_t * restrict L, struct fraction * restrict Faux, bool signed_scale) {
float max = 0.0f;
float amax = 0.0f;
for (int i = 0; i < n; ++i) {
float ax = fabsf(x[i]);
if (ax > amax) {
amax = ax;
max = x[i];
}
}
bool negative_scale = false;
if (signed_scale && -nmin != nmax) {
// the max side should have the biggest range
if ((max < 0.0f) == (-nmin < nmax)) {
// [-4, 3] ==> [-3, 4]
int tmp = nmin;
nmin = -nmax;
nmax = -tmp;
negative_scale = true;
static float make_qkxs_quants(int n, int nmin, int nmax, const float * restrict x, const float * restrict weights, int8_t * restrict L, int8_t * restrict Laux, struct fraction * restrict Faux, bool signed_scale) {
const int orig_nmin = nmin;
const int orig_nmax = nmax;
float max = x[0];
float min = x[0];
float w_amax = weights[0] * fabsf(x[0]);
int max_i = 0;
int w_amax_i = 0;
int min_i = 0;
for (int i = 1; i < n; ++i) {
if (x[i] < min) { min = x[i]; min_i = i; }
if (x[i] > max) { max = x[i]; max_i = i; }
// Find the most important value
const float w = weights[i];
const float wax = w * fabsf(x[i]);
if (wax > w_amax) {
w_amax = wax;
w_amax_i = i;
}
}
const int amax_i = fabsf(min) > fabsf(max) ? min_i : max_i;
const float amax = fabsf(x[amax_i]);
if (amax < GROUP_MAX_EPS) { // all zero
for (int i = 0; i < n; ++i) {
L[i] = 0;
}
return 0.0f;
}
bool negative_scale = false;
if (signed_scale && -nmin != nmax) {
// the max side should have the biggest range
// FIXME: this is incorrect when the weights[.] do not sort in the same order as fabsf(x[.])
// or is it some other condition?
if ((x[amax_i] < 0.0f) == (-nmin < nmax)) {
// [-4, 3] ==> [-3, 4]
const int tmp = nmin;
const float ftmp = min;
nmin = -nmax;
nmax = -tmp;
min = -max;
max = -ftmp;
negative_scale = true;
}
}
// Find the max range in [0, amax_range] which doesn't result in clamping.
// This is the range from the side which would clamp first (biggest ratio of max to nmax).
int amax_range;
float range_max;
if (fabsf(-max * nmin) < fabsf(-min * nmax)) {
amax_range = MAX(0, -nmin);
range_max = fabsf(min);
} else {
amax_range = MAX(0, nmax);
range_max = fabsf(max);
}
float sumlx = 0.0f;
float suml2 = 0.0f;
float scale = 0.0f;
float best = 0.0f;
float best_denom = 1.0f;
if (amax_range > 1) {
// The smallest non-redundant iscale makes the first clamped value half+1 its max integer value.
// Proof: anything smaller has a representable vector with values twice as big.
const float iscale = ((float)(amax_range / 2 + 1))/range_max * (negative_scale ? -1.0f : 1.0f);
for (int i = 0; i < n; ++i) {
const float w = weights[i];
int l = MAX(nmin, MIN(lroundf(x[i] * iscale), nmax));
if (negative_scale) { l = -l; }
Laux[i] = l;
L[i] = l;
suml2 += w * l * l;
sumlx += w * l * x[i];
}
best = sumlx * sumlx;
best_denom = suml2; // should never be zero
scale = sumlx / suml2;
} else {
for (int i = 0; i < n; ++i) {
Laux[i] = 0;
L[i] = 0;
}
}
const int imax_range = MAX(0, (x[w_amax_i] < 0.0f) ? -nmin : nmax);
const int max_odd = 2*(imax_range + 1) + 1;
const float wmax = fabsf(x[w_amax_i]);
int n_frac = 0;
for (int i = 0; i < n; ++i) {
// assuming nmin <= nmax
const int odd_max = MAX(0, x[i] < 0 ? -nmin : nmax);
const int odd_min = MAX(0, x[i] < 0 ? -nmax : nmin);
const int odd_max = MAX(abs(Laux[i]), x[i] < 0.0f ? -nmin : nmax);
const int odd_min = MAX(abs(Laux[i]), x[i] < 0.0f ? -nmax : nmin);
const float v = fabsf(x[i]);
// fprintf(stderr, "%s: i=%d, odd_min=%d, odd_max=%d\n", __func__, i, odd_min, odd_max);
const float v_max_odd = v * max_odd;
for (int j = odd_min; j < odd_max; ++j) {
const float odd = 2*j + 1;
if (wmax * odd < v_max_odd) {
Faux[n_frac++] = (struct fraction){
.numer=v,
.denom=odd,
.i=i,
};
} else {
// stop when the inverse scale would result in clamping the max (FIXME: most important) value
break;
}
}
}
qsort(Faux, n_frac, sizeof(struct fraction), compare_fractions_desc);
float iscale = 0.0f;
{
float sumlx = 0.0f;
float suml2 = 0.0f;
float best = 0.0f;
float best_denom = 1.0f;
int best_p_i = -1; // consecutive with 0..n_frac
for (int i = 0; i < n_frac; ++i) {
// maximize the weighted cosine
const int ii = Faux[i].i;
@@ -719,38 +780,28 @@ static float make_qkxs_quants(int n, int nmin, int nmax, const float * restrict
sumlx += w * Faux[i].numer;
suml2 += w * Faux[i].denom;
const float current = sumlx * sumlx;
// fprintf(stderr, "%s: Faux[%d]=(%f/%f) * %f, square(sumlx)=%f, suml2=%f, k*cos2=%f\n", __func__, i, Faux[i].numer, Faux[i].denom, Faux[i].weight, current, suml2, current / suml2);
// use the last in case of equality
// FIXME: > or >= ?? Why does [0, 0, 1] rounds to [0, 0, 0] with >= ?
if (suml2 > 0.0f && current * best_denom > best * suml2) {
Laux[ii] += x[ii] < 0.0f ? -1 : 1;
if (suml2 > 0.0f && Faux[i].numer > 0.0f && current * best_denom > best * suml2) {
best = current;
best_denom = suml2;
iscale = Faux[i].numer > 0.0f ? Faux[i].denom / (2.0f * Faux[i].numer) : 0.0f;
if (!isfinite(iscale)) {
fprintf(stderr, "%s: iscale is not finite, %f/(2*%f)\n", __func__, Faux[i].denom, Faux[i].numer);
scale = sumlx / suml2;
if (i == best_p_i + 1) {
// reduce copies for consecutive bests
L[ii] += x[ii] < 0.0f ? -1 : 1;
} else {
for (int j = 0; j < n; ++j) {
L[j] = Laux[j];
}
}
best_p_i = i;
}
}
// (very) small fudging necessary because floats otherwise round to nearest even
iscale = iscale * ((float)((1 << 23) + 1) / (float)(1 << 23));
float sumlx = 0.0f;
float suml2 = 0.0f;
for (int i = 0; i < n; ++i) {
// Rounding away from zero is assumed by the search algorithm above.
int l = MAX(nmin, MIN(lroundf(x[i] * iscale), nmax));
if (negative_scale) {
l = -l;
}
L[i] = negative_scale ? l + nmax : l - nmin;
float w = weights ? weights[i] : x[i] * x[i];
// weighted projection scale
sumlx += w * x[i] * l;
suml2 += w * l * l;
L[i] = negative_scale ? (-L[i] + nmax) : (L[i] + -nmin);
GGML_ASSERT(L[i] >= 0 && L[i] <= nmax - nmin);
}
return suml2 > 0.0f ? sumlx / suml2 : 0.0f;
return negative_scale ? -scale : scale;
}
// non-linear exhaustive search with cumulative sums
@@ -1234,6 +1285,7 @@ void quantize_row_q3_K_ref(const float * restrict x, block_q3_K * restrict y, in
const int nb = k / QK_K;
int8_t L[QK_K];
int8_t Laux[16];
struct fraction Faux[16 * 4];
float scales[QK_K / 16];
float weights[16];
@@ -1247,7 +1299,7 @@ void quantize_row_q3_K_ref(const float * restrict x, block_q3_K * restrict y, in
float max_scale = 0;
float amax = 0;
for (int j = 0; j < QK_K/16; ++j) {
scales[j] = make_qkxs_quants(16, -4, 3, x + 16*j, weights, L + 16*j, Faux, true);
scales[j] = make_qkxs_quants(16, -4, 3, x + 16*j, weights, L + 16*j, Laux, Faux, true);
// scales[j] = make_q3_quants(16, 4, x + 16*j, L + 16*j, true);
float scale = fabsf(scales[j]);
if (scale > amax) {
@@ -1367,6 +1419,7 @@ static void quantize_row_q3_K_impl(const float * restrict x, block_q3_K * restri
const int nb = n_per_row / QK_K;
int8_t L[QK_K];
int8_t Laux[16];
float scales[QK_K / 16];
float weight[16];
float sw[QK_K / 16];
@@ -1391,14 +1444,14 @@ static void quantize_row_q3_K_impl(const float * restrict x, block_q3_K * restri
sw[j] = sumw;
// scales[j] = make_qx_quants(16, 4, x + 16*j, L + 16*j, 1, weight);
scales[j] = make_qkxs_quants(16, -4, 3, x + 16*j, weight, L + 16*j, Faux, true);
scales[j] = make_qkxs_quants(16, -4, 3, x + 16*j, weight, L + 16*j, Laux, Faux, true);
}
memset(y[i].scales, 0, 12);
// float d_block = make_qx_quants(QK_K/16, 32, scales, Ls, 1, sw);
float d_block = make_qkxs_quants(QK_K/16, -32, 31, scales, sw, Ls, Faux, true);
float d_block = make_qkxs_quants(QK_K/16, -32, 31, scales, sw, Ls, Laux, Faux, true);
for (int j = 0; j < QK_K/16; ++j) {
int l = Ls[j];
if (j < 8) {
@@ -4856,11 +4909,11 @@ static void quantize_row_iq4_nl_impl(const int super_block_size, const int block
for (int j = 0; j < block_size; ++j) weight[j] = sqrtf(sigma2 + xb[j]*xb[j]);
// for (int j = 0; j < block_size; ++j) weight[j] = 1;
}
float amax = 0, max = 0;
float amax = 0;
for (int j = 0; j < block_size; ++j) {
float ax = fabsf(xb[j]);
if (ax > amax) {
amax = ax; max = xb[j];
amax = ax;
}
}
if (amax < GROUP_MAX_EPS) {