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Fix known issues in mha cpp api #1966

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Fix known issues in mha cpp api #1966

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26 changes: 14 additions & 12 deletions csrc/cpp_itfs/mha_bwd.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -9,21 +9,23 @@ std::tuple<int, int> get_padded_hdim(int hdim_q, int hdim_v, std::string arch_id
{
if(hdim_q == 192 && hdim_v == 128 && arch_id == "gfx950")
return std::make_tuple(hdim_q, hdim_v);
assert(hdim_q == hdim_v);
if(hdim_q <= 64)
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Copilot AI Feb 4, 2026

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This line contains only whitespace. Remove the trailing whitespace for cleaner code formatting.

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if(hdim_q == hdim_v)
{
return std::make_tuple(64, 64);
}
else if(hdim_q <= 128)
{
return std::make_tuple(128, 128);
}
else if(hdim_q <= 192)
{
return std::make_tuple(192, 192);
if(hdim_q <= 64)
{
return std::make_tuple(64, 64);
}
else if(hdim_q <= 128)
{
return std::make_tuple(128, 128);
}
else if(hdim_q <= 192)
{
return std::make_tuple(192, 192);
}
}

assert(false);
return std::make_tuple(hdim_q, hdim_v);
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When hdim_q != hdim_v and the special case (hdim_q == 192 && hdim_v == 128) is not met, the function returns unpadded dimensions without any validation or error handling. This silently allows unsupported dimension combinations to proceed, which could lead to runtime errors. Consider adding validation or error handling for unsupported dimension pairs.

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}

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4 changes: 2 additions & 2 deletions op_tests/cpp/mha/benchmark_mha_fwd.cpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
// SPDX-License-Identifier: MIT
// Copyright (C) 2018-2025, Advanced Micro Devices, Inc. All rights reserved.
// Copyright (C) 2018-2026, Advanced Micro Devices, Inc. All rights reserved.
#include "ck_tile/host.hpp"
#include "ck_tile/ref/naive_attention.hpp"
#include "mha_fwd.h"
Expand Down Expand Up @@ -1144,7 +1144,7 @@ bool run(const ck_tile::ArgParser& arg_parser)

auto oacc_element_func = [&]() {
if constexpr(std::is_same_v<DataTypeConfig, ck_tile::fp8_t>)
return ck_tile::composes(ck_tile::saturates<ck_tile::fp8_t>{},
return ck_tile::make_composes(ck_tile::saturates<ck_tile::fp8_t>{},
ck_tile::scales{scale_o});
else
return ck_tile::identity{};
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