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metal : clamp K extent in tensor API mat-mat kernel #27450

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Merged
ggerganov merged 1 commit into from
Aug 20, 2026
Merged

metal : clamp K extent in tensor API mat-mat kernel #27450

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15 changes: 11 additions & 4 deletions ggml/src/ggml-metal/ggml-metal.metal
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Original file line number Diff line number Diff line change
Expand Up @@ -10365,9 +10365,12 @@ kernel void kernel_mul_mm(
auto tB = tensor(ptrB, dextents<int32_t, 2>(K, N), array<int, 2>({1, strideB}));

// Configure matmul operation
// note: K is dynamic_extent (clamped to the valid range in PHASE 2), since a static
// N_MM_NK_TOTAL K tile would read src1 out of bounds when K % N_MM_NK_TOTAL != 0
// ref: https://github.com/ggml-org/llama.cpp/pull/27064
mpp::tensor_ops::matmul2d<
mpp::tensor_ops::matmul2d_descriptor(
NRB, NRA, N_MM_NK_TOTAL, false, true, true,
NRB, NRA, static_cast<int>(dynamic_extent), false, true, true,
mpp::tensor_ops::matmul2d_descriptor::mode::multiply_accumulate),
execution_simdgroups<N_MM_SIMD_GROUP_X * N_MM_SIMD_GROUP_Y>> mm;

Expand Down Expand Up @@ -10419,10 +10422,14 @@ kernel void kernel_mul_mm(
threadgroup_barrier(mem_flags::mem_threadgroup);

// === PHASE 2: Tensor matmul ===
auto mA = tA.slice(0, 0);
auto mB = tB.slice(loop_k, rb);
// Clamp the K extent of both operand tensors to the remaining valid K range so
// the dynamic-K op never reads past the K extent of src1 (or the staged A tile).
const int kExt = min(N_MM_NK_TOTAL, K - loop_k);

mm.run(mB, mA, cT);
auto tAv = tensor(sa, dextents<int32_t, 2>(kExt, NRA), array<int, 2>({1, N_MM_NK_TOTAL}));
auto tBv = tensor(ptrB + loop_k + rb * strideB, dextents<int32_t, 2>(kExt, N - rb), array<int, 2>({1, strideB}));

mm.run(tBv, tAv, cT);

threadgroup_barrier(mem_flags::mem_threadgroup);
}
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8 changes: 8 additions & 0 deletions tests/test-backend-ops.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9298,6 +9298,14 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {

test_cases.emplace_back(new test_mul_mat(GGML_TYPE_Q8_0, GGML_TYPE_F32, 6, 4096, 5120, {1, 1}, {1, 1}));

// K not a multiple of 32
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F16, 64, 32, 65, {1, 1}, {1, 1}));
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F16, 64, 32, 80, {1, 1}, {1, 1}));
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F32, 64, 32, 80, {1, 1}, {1, 1}));
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F32, GGML_TYPE_F32, 64, 32, 80, {1, 1}, {1, 1}));
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F16, 64, 32, 588, {1, 1}, {1, 1})); // 14*14*3, e.g. conv_2d im2col
test_cases.emplace_back(new test_mul_mat(GGML_TYPE_F16, GGML_TYPE_F16, 64, 32, 80, {4, 1}, {1, 1}));

#if 0
// test the mat-mat path for Metal
for (int k = 1; k < 512; ++k) {
Expand Down
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