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Precise sigmoid (#2659)

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* bump patch

* Sigmoid matches PyTorch and is more precise on tails
This commit is contained in:
Awni Hannun
2025-10-10 10:05:23 -07:00
committed by GitHub
parent 380aeb58ae
commit 630350ad3e
4 changed files with 12 additions and 5 deletions
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3
mlx/backend/cpu/unary_ops.h
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@@ -77,7 +77,8 @@ struct Real {
struct Sigmoid {
template <int N, typename T>
Simd<T, N> operator()(Simd<T, N> x) {
return 1.0f / (1.0f + simd::exp(-x));
auto y = 1.0f / (1.0f + simd::exp(simd::abs(x)));
return simd::select(x < Simd<T, N>{0}, y, Simd<T, N>{1} - y);
}
SINGLE()
};

4
mlx/backend/cuda/device/unary_ops.cuh
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@@ -257,8 +257,8 @@ struct Round {
struct Sigmoid {
template <typename T>
__device__ T operator()(T x) {
T y = 1 / (1 + exp(-abs(x)));
return (x < 0) ? 1 - y : y;
T y = 1 / (1 + exp(abs(x)));
return (x < 0) ? y : 1 - y;
}
};

4
mlx/backend/metal/kernels/unary_ops.h
View File

@@ -309,8 +309,8 @@ struct Round {
struct Sigmoid {
template <typename T>
T operator()(T x) {
auto y = 1 / (1 + metal::exp(-metal::abs(x)));
return (x < 0) ? 1 - y : y;
auto y = 1 / (1 + metal::exp(metal::abs(x)));
return (x < 0) ? y : 1 - y;
}
};