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metal : add Q4_K implementation (#1733)

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* Metal implementation for Q4_K

Very slow for now:
42 ms / token, Q4_0 runs in 28 ms/token on my
30-core M2 Max GPU.

* Optimizing Q4_K on metal

The first token always takes longer, I guess because
the metal kernel is being jit-compiled.
So, using n = 128 to measure time.

At this point Q4_K takes 29.5 ms / token
compared to 27.2 ms / token for Q4_0.
Quite a bit better than the initial attempt,
but still not good enough.

* Optimizing q4_K metal dot some more

For n = 256 it is now 28.1 ms/token compared to
27 ms/token for q4_0.

* Fix after merge with master

---------

Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>
This commit is contained in:
Kawrakow 2023-06-08 10:08:23 +03:00 • committed by GitHub
parent 0035858273
commit 4161bdc04d
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3 changed files with 184 additions and 19 deletions
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@ -503,3 +503,165 @@ kernel void kernel_cpy_f32_f32(
dst_data[i00] = src[0];
}
}
//============================================ k-quants ======================================================
#define QK_K 256
typedef struct {
half d; // super-block scale for quantized scales
half dmin; // super-block scale for quantized mins
uint8_t scales[3*QK_K/64]; // scales and mins, quantized with 6 bits
uint8_t qs[QK_K/2]; // 4--bit quants
} block_q4_k;
static inline uchar4 get_scale_min_k4(int j, device const uint8_t * q) {
uchar4 r;
if (j < 4) {
r[0] = q[j+0] & 63; r[1] = q[j+4] & 63;
r[2] = q[j+1] & 63; r[3] = q[j+5] & 63;
} else {
r[0] = (q[j+4] & 0xF) | ((q[j-4] >> 6) << 4);
r[1] = (q[j+4] >> 4) | ((q[j-0] >> 6) << 4);
r[2] = (q[j+5] & 0xF) | ((q[j-3] >> 6) << 4);
r[3] = (q[j+5] >> 4) | ((q[j+1] >> 6) << 4);
}
return r;
}
static void dequantize_row_q4_k(device const block_q4_k * x, device float * y, int k) {
assert(k % QK_K == 0);
const int nb = k / QK_K;
for (int i = 0; i < nb; i++) {
const float d = x[i].d;
const float min = x[i].dmin;
device const uint8_t * q = x[i].qs;
device const uint8_t * scales = x[i].scales;
int is = 0;
for (int j = 0; j < QK_K; j += 64) {
const uchar4 sc = get_scale_min_k4(is, scales);
const float d1 = d * sc[0]; const float m1 = min * sc[1];
const float d2 = d * sc[2]; const float m2 = min * sc[3];
for (int l = 0; l < 32; ++l) *y++ = d1 * (q[l] & 0xF) - m1;
for (int l = 0; l < 32; ++l) *y++ = d2 * (q[l] >> 4) - m2;
q += 32; is += 2;
}
}
}
kernel void kernel_get_rows_q4_k(
device const void * src0,
device const int * src1,
device float * dst,
constant int64_t & ne00,
constant uint64_t & nb01,
constant uint64_t & nb1,
uint tpig[[thread_position_in_grid]]) {
const int i = tpig;
const int r = ((device int32_t *) src1)[i];
dequantize_row_q4_k(
(device const block_q4_k *) ((device char *) src0 + r*nb01),
(device float *) ((device char *) dst + i*nb1), ne00);
}
kernel void kernel_mul_mat_q4_k_f32(
device const void * src0,
device const float * src1,
device float * dst,
constant int64_t & ne00,
constant int64_t & ne01,
constant uint64_t & nb00,
constant uint64_t & nb01,
constant uint64_t & nb02,
constant int64_t & ne10,
constant int64_t & ne11,
constant uint64_t & nb10,
constant uint64_t & nb11,
constant uint64_t & nb12,
constant int64_t & ne0,
constant int64_t & ne1,
threadgroup float * sum [[threadgroup(0)]],
uint2 tgpig[[threadgroup_position_in_grid]],
uint2 tpig[[thread_position_in_grid]], // we don't use this for now
uint2 tpitg[[thread_position_in_threadgroup]],
uint2 tptg[[threads_per_threadgroup]]) {
const int nb = ne00/QK_K;
const int64_t r0 = tgpig.x;
const int64_t r1 = tgpig.y;
device const block_q4_k * x = (device const block_q4_k *) src0 + r0*nb;
device const float * yy = (device const float *) src1 + r1*ne10;
const uint nth = tptg.x*tptg.y;
const uint ith = tptg.y*tpitg.x + tpitg.y;
const int tid = tpitg.y; // 0...16
const int il = tid/4; // 0...3
const int ir = tid%4; // 0...3
const int n = 8;
const int is = 2*il;
sum[ith] = 0.0f;
float sumf = 0;
for (int i = tpitg.x; i < nb; i += tptg.x) {
device const uint8_t * q = (x + i)->qs + 32*il + n*ir;
device const float * y = yy + i*QK_K + 64*il + n*ir;
device const uint8_t * scales = (x + i)->scales;
const float dall = (float)((x + i)->d);
const float dmin = (float)((x + i)->dmin);
const uchar4 sc = get_scale_min_k4(is, scales);
float4 s = {0.f, 0.f, 0.f, 0.f};
for (int l = 0; l < n; ++l) {
s[0] += y[l+ 0] * (q[l] & 0xF); s[1] += y[l+ 0];
s[2] += y[l+32] * (q[l] >> 4); s[3] += y[l+32];
}
sumf += dall * (s[0] * sc[0] + s[2] * sc[2]) - dmin * (s[1] * sc[1] + s[3] * sc[3]);
}
sum[ith] = sumf;
//
// Accumulate the sum from all threads in the threadgroup
// This version is slightly faster than the commented out one below,
// which I copy-pasted from ggerganov's q4_0 dot product for metal.
//
threadgroup_barrier(mem_flags::mem_threadgroup);
if (ith%4 == 0) {
for (int i = 1; i < 4; ++i) sum[ith] += sum[ith + i];
}
threadgroup_barrier(mem_flags::mem_threadgroup);
if (ith%16 == 0) {
for (int i = 4; i < 16; i += 4) sum[ith] += sum[ith + i];
}
threadgroup_barrier(mem_flags::mem_threadgroup);
if (ith == 0) {
for (int i = 16; i < nth; i += 16) sum[0] += sum[i];
dst[r1*ne0 + r0] = sum[0];
}
//// accumulate the sum from all threads in the threadgroup
//threadgroup_barrier(mem_flags::mem_threadgroup);
//for (uint i = nth/2; i > 0; i /= 2) {
// if (ith < i) {
// sum[ith] += sum[ith + i];
// }
// threadgroup_barrier(mem_flags::mem_threadgroup);
//}
//if (ith == 0) {
// dst[r1*ne0 + r0] = sum[0];
//}
}