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ggml-webgpu: tune subgroup split (d_split) in flash_attn_vec (#25418)

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This commit is contained in:
Masashi Yoshimura
2026-07-09 08:34:19 +09:00
committed by GitHub
parent 92366df30d
commit 32e41fa5b4
2 changed files with 16 additions and 23 deletions
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ggml/src/ggml-webgpu/ggml-webgpu-shader-lib.hpp
+9 -16
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@@ -2821,23 +2821,16 @@ class ggml_webgpu_shader_lib {
variant.resize(variant.size() - (sizeof("_mask") - 1));
variant += "_mask_blk";
}
uint32_t vec_ne = 1u;
if (key.common.k_type == GGML_TYPE_F16 && key.common.v_type == GGML_TYPE_F16 &&
key.common.head_dim_qk == key.common.head_dim_v) {
switch (key.common.head_dim_qk) {
case 64:
case 192:
case 576:
vec_ne = 2u;
break;
case 96:
vec_ne = 4u;
break;
default:
break;
}
uint32_t d_split = context.min_subgroup_size;
if (key.common.k_type == GGML_TYPE_F16 && key.common.v_type == GGML_TYPE_F16) {
const uint32_t D = key.common.head_dim_qk | key.common.head_dim_v;
const uint32_t D_lsb = D & (~(D - 1u));
d_split = std::min(std::min(context.min_subgroup_size, 4u), std::max(D_lsb / 4u, 1u));
}
defines.push_back(std::string("VEC_NE=") + std::to_string(vec_ne) + "u");
defines.push_back(std::string("D_SPLIT=") + std::to_string(d_split));
variant += "_dsplit" + std::to_string(d_split);
auto pipeline_decisions = std::make_shared<ggml_webgpu_flash_attn_vec_decisions>(decisions);
webgpu_pipeline pipeline =