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Refactor CPU Softmax dtype dispatch #4127

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Merged
zcbenz merged 1 commit into from
Aug 10, 2026
Merged

Refactor CPU Softmax dtype dispatch #4127

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34 changes: 13 additions & 21 deletions mlx/backend/cpu/softmax.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
#include "mlx/backend/cpu/copy.h"
#include "mlx/backend/cpu/encoder.h"
#include "mlx/backend/cpu/simd/simd.h"
#include "mlx/dtype_utils.h"
#include "mlx/primitives.h"
#include "mlx/types/limits.h"

Expand Down Expand Up @@ -139,32 +140,23 @@ void Softmax::eval_cpu(const std::vector<array>& inputs, array& out) {

auto in = set_output(inputs[0]);

switch (in.dtype()) {
case float32:
softmax<float, float>(in, out, stream());
break;
case float16:
dispatch_all_types(in.dtype(), [&](auto type_tag) {
using T = MLX_GET_TYPE(type_tag);
if constexpr (
std::is_same_v<T, float16_t> || std::is_same_v<T, bfloat16_t>) {
if (precise_) {
softmax<float16_t, float>(in, out, stream());
softmax<T, float>(in, out, stream());
} else {
softmax<float16_t, float16_t>(in, out, stream());
softmax<T, T>(in, out, stream());
}
break;
case bfloat16:
if (precise_) {
softmax<bfloat16_t, float>(in, out, stream());
} else {
softmax<bfloat16_t, bfloat16_t>(in, out, stream());
}
break;
case float64:
softmax<double, double>(in, out, stream());
break;
default:
} else if constexpr (
std::is_same_v<T, float> || std::is_same_v<T, double>) {
softmax<T, T>(in, out, stream());
} else {
throw std::runtime_error(
"[softmax] Only defined for floating point types.");
break;
}
}
});
}

} // namespace mlx::core
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