File size: 4,772 Bytes
b664585 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 |
#version 450
#extension GL_EXT_shader_explicit_arithmetic_types_float16 : require
#extension GL_EXT_control_flow_attributes : enable
layout (push_constant) uniform parameter
{
uint KX;
uint KY;
float scale;
float max_bias;
float m0;
float m1;
uint n_head_log2;
uint nrows_x;
} p;
#include "types.comp"
layout(constant_id = 0) const uint BLOCK_SIZE = 32;
layout(local_size_x_id = 0, local_size_y = 1, local_size_z = 1) in;
layout (binding = 0) readonly buffer X {A_TYPE data_a[];};
layout (binding = 1) readonly buffer Y {B_TYPE data_b[];};
layout (binding = 2) buffer D {D_TYPE data_d[];};
shared FLOAT_TYPE vals[BLOCK_SIZE];
// num_iters is the number of BLOCK_SIZE loop iterations we need to iterate
// over all the columns. The main function tries to pass a constant here,
// as if it were a template function, to allow unrolling.
void soft_max(uint num_iters) {
const uint tid = gl_LocalInvocationID.x;
const uint rowx = gl_WorkGroupID.z * 262144 + gl_WorkGroupID.y * 512 + gl_WorkGroupID.x;
const uint rowy = rowx % p.KY;
if (rowx >= p.nrows_x) {
return;
}
float slope = 1.0f;
// ALiBi
if (p.max_bias > 0.0f) {
const uint h = rowx/p.KY; // head index
const float base = h < p.n_head_log2 ? p.m0 : p.m1;
const uint exp = h < p.n_head_log2 ? h + 1 : 2*(h - p.n_head_log2) + 1;
slope = pow(base, exp);
}
// Find max
FLOAT_TYPE max_val = uintBitsToFloat(0xFF800000);
// Cache values while we compute the max, so we don't need to read them
// again when we're ready to compute exp(x-max).
const uint DATA_CACHE_SIZE = 16;
FLOAT_TYPE data_cache[DATA_CACHE_SIZE];
[[unroll]] for (uint col0 = 0, idx = 0; idx < num_iters; col0 += BLOCK_SIZE, ++idx) {
const uint col = col0 + tid;
FLOAT_TYPE a = FLOAT_TYPE(0);
if (col < p.KX) {
a = data_a[rowx * p.KX + col];
}
FLOAT_TYPE b = FLOAT_TYPE(0);
if (p.KY > 0 && col < p.KX) {
b = data_b[rowy * p.KX + col];
}
FLOAT_TYPE v = a * p.scale + slope * b;
if (col < p.KX) {
max_val = max(max_val, v);
}
if (idx < DATA_CACHE_SIZE) {
data_cache[idx] = v;
}
}
// reduce across the workgroup
vals[tid] = max_val;
barrier();
[[unroll]] for (uint s = BLOCK_SIZE / 2; s > 0; s >>= 1) {
if (tid < s) {
vals[tid] = max(vals[tid], vals[tid + s]);
}
barrier();
}
max_val = vals[0];
barrier();
FLOAT_TYPE sum = FLOAT_TYPE(0.0f);
// Compute sum{exp(x - max)}
[[unroll]] for (uint col0 = 0, idx = 0; idx < num_iters; col0 += BLOCK_SIZE, ++idx) {
const uint col = col0 + tid;
if (col >= p.KX) {
break;
}
// compute exp(a*scale+b*slope), add it to sum, and cache the new value
// in data_cache if possible.
const uint i = rowx * p.KX + col;
FLOAT_TYPE val;
if (idx < DATA_CACHE_SIZE) {
val = exp(data_cache[idx] - max_val);
} else {
val = exp(FLOAT_TYPE(data_a[i]) * p.scale + (p.KY > 0 ? slope * FLOAT_TYPE(data_b[rowy * p.KX + col]) : FLOAT_TYPE(0.0f)) - max_val);
}
sum += val;
if (idx < DATA_CACHE_SIZE) {
data_cache[idx] = val;
} else {
data_d[i] = D_TYPE(val);
}
}
// reduce across the workgroup
vals[tid] = sum;
barrier();
[[unroll]] for (uint s = BLOCK_SIZE / 2; s > 0; s >>= 1) {
if (tid < s) {
vals[tid] += vals[tid + s];
}
barrier();
}
sum = vals[0];
FLOAT_TYPE rcpdivisor = 1.0/sum;
[[unroll]] for (uint col0 = 0, idx = 0; idx < num_iters; col0 += BLOCK_SIZE, ++idx) {
const uint col = col0 + tid;
if (col >= p.KX) {
continue;
}
if (idx < DATA_CACHE_SIZE) {
data_d[rowx*p.KX + col] = D_TYPE(data_cache[idx] * rcpdivisor);
} else {
data_d[rowx*p.KX + col] *= D_TYPE(rcpdivisor);
}
}
}
void main() {
// instantiate the soft_max function for several different
// dimensions, to allow loop unrolling
uint num_blocks = (p.KX + BLOCK_SIZE - 1) / BLOCK_SIZE;
if (num_blocks > 32) {
soft_max(num_blocks);
} else if (num_blocks > 16) {
soft_max(32);
} else if (num_blocks > 8) {
soft_max(16);
} else if (num_blocks > 4) {
soft_max(8);
} else if (num_blocks == 4) {
soft_max(4);
} else if (num_blocks == 3) {
soft_max(3);
} else if (num_blocks == 2) {
soft_max(2);
} else if (num_blocks == 1) {
soft_max(1);
}
}
|