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vulkan: skip all-negative-inf blocks in FA (#17186)

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This commit is contained in:
Jeff Bolz
2025-11-15 10:37:25 +01:00
committed by GitHub
parent 38eaf32af1
commit 234ae7d7bd
4 changed files with 116 additions and 43 deletions
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ggml/src/ggml-vulkan/vulkan-shaders/flash_attn.comp
+33 -15
View File
@@ -7,6 +7,7 @@
#extension GL_EXT_shader_explicit_arithmetic_types_int32 : require
#extension GL_KHR_shader_subgroup_shuffle : enable
#extension GL_KHR_shader_subgroup_vote : enable
#include "types.glsl"
#include "flash_attn_base.glsl"
@@ -108,6 +109,38 @@ void main() {
[[dont_unroll]]
for (uint32_t j = start_j; j < end_j; ++j) {
if ((p.mask_n_head_log2 & MASK_ENABLE_BIT) != 0) {
bool nem1_bounds_check = !(p.gqa_ratio > 1) && (p.nem1 % Br) != 0;
float max_mask = NEG_FLT_MAX_OVER_2;
[[unroll]] for (uint32_t idx = 0; idx < Bc * Br; idx += gl_WorkGroupSize.x) {
uint32_t c = (idx + tid) % Bc;
uint32_t r = (idx + tid) / Bc;
if (idx + tid < Bc * Br) {
if ((!KV_bounds_check || j * Bc + c < KV) && (!nem1_bounds_check || i * Br + r < p.nem1)) {
float m = float(data_m[m_offset + (i * Br + r) * m_stride + (j * Bc + c)]);
masksh[c][r] = m;
max_mask = max(max_mask, m);
} else {
masksh[c][r] = float(0);
}
}
}
// skip the block if the mask is entirely -inf
bool all_less = subgroupAll(max_mask <= NEG_FLT_MAX_OVER_2);
barrier();
if (gl_SubgroupInvocationID == 0) {
tmpsh[gl_SubgroupID] = all_less ? NEG_FLT_MAX_OVER_2 : 0.0f;
}
barrier();
[[unroll]] for (uint s = 0; s < gl_NumSubgroups; ++s) {
max_mask = max(max_mask, tmpsh[s]);
}
if (max_mask <= NEG_FLT_MAX_OVER_2) {
continue;
}
}
float Sf[Br][cols_per_thread];
[[unroll]] for (uint32_t r = 0; r < Br; ++r) {
[[unroll]] for (uint32_t c = 0; c < cols_per_thread; ++c) {
@@ -153,21 +186,6 @@ void main() {
}
if ((p.mask_n_head_log2 & MASK_ENABLE_BIT) != 0) {
bool nem1_bounds_check = !(p.gqa_ratio > 1) && (p.nem1 % Br) != 0;
[[unroll]] for (uint32_t idx = 0; idx < Bc * Br; idx += gl_WorkGroupSize.x) {
uint32_t c = (idx + tid) % Bc;
uint32_t r = (idx + tid) / Bc;
if (idx + tid < Bc * Br) {
if ((!KV_bounds_check || j * Bc + c < KV) && (!nem1_bounds_check || i * Br + r < p.nem1)) {
masksh[c][r] = float(data_m[m_offset + (i * Br + r) * m_stride + (j * Bc + c)]);
} else {
masksh[c][r] = float(0);
}
}
}
barrier();
[[unroll]] for (uint32_t c = 0; c < cols_per_thread; ++c) {
[[unroll]] for (uint32_t r = 0; r < Br; ++r) {
float mvf = masksh[c * cols_per_iter + col_tid][r];