add SiLU activation function

dfdx-core/src/tensor_ops/mod.rs

@@ -197,6 +197,7 @@ mod roll;
 mod select_and_gather;
 mod sgd;
 mod sigmoid;
+mod silu;
 mod sin;
 mod slice;
 mod softmax;
@@ -264,6 +265,7 @@ pub use roll::Roll;
 pub use select_and_gather::{GatherTo, SelectTo};
 pub use sgd::SgdConfig;
 pub use sigmoid::sigmoid;
+pub use silu::silu;
 pub use sin::sin;
 pub use slice::slice;
 pub use softmax::softmax;

dfdx-core/src/tensor_ops/silu/cpu_kernel.rs

@@ -0,0 +1,20 @@
+use crate::tensor_ops::cpu_kernels::UnaryDerivative;
+
+impl<F: num_traits::Float> UnaryDerivative<F> for super::SiLUKernelOp {
+    const DF_USES_FX: bool = false;
+    const HAS_CONST_DF: bool = false;
+
+    // x / (1 + e^-x)
+    #[inline(always)]
+    fn f(&self, x: &F) -> F {
+        *x / (F::one() + x.neg().exp())
+    }
+
+    // (1 + e^-x + x * e^-x) / (1 + e^-x)^2
+    // alternative: (e^x (1 + e^x + x)) / (1 + e^x)^2
+    #[inline(always)]
+    fn df(&self, x: &F) -> F {
+        let exp_nx = x.neg().exp();
+        F::one() + exp_nx + *x * exp_nx / (F::one() + exp_nx).powi(2)
+    }
+}

dfdx-core/src/tensor_ops/silu/cuda_kernel.rs

@@ -0,0 +1,15 @@
+use super::SiLUKernelOp;
+#[allow(unused_imports)]
+use crate::dtypes::*;
+use crate::tensor_ops::cuda_kernels::cuda_unary;
+
+unsafe impl cudarc::driver::DeviceRepr for SiLUKernelOp {}
+
+const PTX: &str = include_str!(concat!(env!("OUT_DIR"), "/silu.ptx"));
+
+#[cfg(feature = "f16")]
+cuda_unary!(SiLUKernelOp, f16, PTX, "silu_fwd_f16", "silu_bwd_f16");
+#[cfg(feature = "f16")]
+cuda_unary!(SiLUKernelOp, AMP<f16>, PTX, "silu_fwd_f16", "silu_bwd_f16");
+cuda_unary!(SiLUKernelOp, f32, PTX, "silu_fwd_f32", "silu_bwd_f32");
+cuda_unary!(SiLUKernelOp, f64, PTX, "silu_fwd_f64", "silu_bwd_f64");

dfdx-core/src/tensor_ops/silu/mod.rs

@@ -0,0 +1,62 @@
+mod cpu_kernel;
+
+#[cfg(feature = "cuda")]
+mod cuda_kernel;
+
+#[cfg(feature = "webgpu")]
+mod webgpu_kernel;
+
+use super::ops::{try_unary_op, UnaryKernel};
+use crate::{shapes::*, tensor::*};
+
+#[repr(C)]
+#[derive(Debug, Default, Copy, Clone)]
+pub struct SiLUKernelOp;
+
+/// [Sigmoid-Weighted Linear Unit (SiLU)](https://en.wikipedia.org/wiki/Rectifier_(neural_networks)). `x * x.sigmoid()`
+///
+/// The derivative is `x * sigmoid'(x) + sigmoid(x)`.
+///
+/// Examples:
+/// ```rust
+/// # use dfdx_core::prelude::*;
+/// # let dev: Cpu = Default::default();
+/// let t = dev.tensor([-1.0, 0.0, 1.0, 2.0]);
+/// let r = t.silu();
+/// ```
+pub fn silu<S: Shape, E: Dtype, D: UnaryKernel<SiLUKernelOp, E>, T: Tape<E, D>>(
+    t: Tensor<S, E, D, T>,
+) -> Tensor<S, E, D, T> {
+    t.silu()
+}
+
+impl<S: Shape, E: Dtype, D: UnaryKernel<SiLUKernelOp, E>, T: Tape<E, D>> Tensor<S, E, D, T> {
+    /// See [silu]
+    pub fn silu(self) -> Self {
+        self.try_silu().unwrap()
+    }
+    /// See [silu]
+    pub fn try_silu(self) -> Result<Self, crate::tensor::Error> {
+        try_unary_op(SiLUKernelOp, self)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{tensor::*, tensor_ops::*, tests::*};
+
+    #[test]
+    fn test_silu() {
+        let dev: TestDevice = Default::default();
+        let x = dev
+            .tensor([-2.0, -1.0, 0.0, 1.0, 2.0])
+            .to_dtype::<TestDtype>();
+        let r = x.leaky_trace().silu();
+        assert_close_to_literal!(r, [-0.23840584, -0.26894143, 0.0, 0.7310586, 1.761594]);
+        let g = r.mean().backward();
+        assert_close_to_literal!(
+            g.get(&x),
+            [1.635814, 0.70433396, 0.4, 0.31289828, 0.26906452]
+        );
+    }
+}

dfdx-core/src/tensor_ops/silu/silu.cu

@@ -0,0 +1,32 @@
+#include "unary_op_macros.cuh"
+
+struct SiLUKernelOp {};
+
+// x / (1 + e^-x)
+template<typename T>
+__device__ __forceinline__ T silu_fwd(T x) {
+    T one = 1.0;
+    return x / (one + expg(-x));
+}
+
+// (1 + e^-x + x * e^-x) / (1 + e^-x)^2
+// alternative: (e^x (1 + e^x + x)) / (1 + e^x)^2
+template<typename T>
+__device__ __forceinline__ T silu_bwd(T x) {
+    T one = 1.0;
+    T exp_nx = expg(-x);
+    T denom_sqrt = (one + exp_nx);
+    return (one + exp_nx + x * exp_nx) / (denom_sqrt * denom_sqrt);
+}
+
+UNARY_OP(__half, silu_fwd_f16, silu_bwd_f16, SiLUKernelOp,
+        silu_fwd(x),
+        silu_bwd(x))
+
+UNARY_OP(float, silu_fwd_f32, silu_bwd_f32, SiLUKernelOp,
+        silu_fwd(x),
+        silu_bwd(x))
+
+UNARY_OP(double, silu_fwd_f64, silu_bwd_f64, SiLUKernelOp,
+        silu_fwd(x),
+        silu_bwd(x))

dfdx-core/src/tensor_ops/silu/webgpu_kernel.rs

@@ -0,0 +1,28 @@
+use std::borrow::Cow;
+
+use crate::prelude::{ops::UnaryKernel, Dtype, Webgpu};
+
+impl<E: Dtype> UnaryKernel<super::SiLUKernelOp, E> for Webgpu {
+    const BACKWARD_WITHOUT_INP: bool = false;
+
+    const BACKWARD_WITHOUT_DATA: bool = false;
+
+    fn forward<S: crate::prelude::Shape>(
+        &self,
+        op: super::SiLUKernelOp,
+        inp: Cow<crate::prelude::Tensor<S, E, Self>>,
+    ) -> Result<crate::prelude::Tensor<S, E, Self>, crate::prelude::Error> {
+        todo!()
+    }
+
+    fn backward<S: crate::prelude::Shape>(
+        &self,
+        op: super::SiLUKernelOp,
+        inp: &impl crate::prelude::Tensorlike<S, E, Self>,
+        grad_inp: &mut Self::Vec,
+        out: &impl crate::prelude::Tensorlike<S, E, Self>,
+        grad_out: &Self::Vec,
+    ) -> Result<(), crate::prelude::Error> {
+        todo!()
+    }
+}

dfdx-core/src/tensor_ops/utilities/device.rs

@@ -92,6 +92,7 @@ pub trait Device<E: Dtype>:
     + UnaryKernel<super::super::fast_gelu::FastGeLUKernelOp, E>
     + UnaryKernel<super::super::accurate_gelu::AccurateGeLUKernelOp, E>
     + UnaryKernel<super::super::sigmoid::SigmoidKernelOp, E>
+    + UnaryKernel<super::super::silu::SiLUKernelOp, E>
     + UnaryKernel<super::super::sin::SinKernelOp, E>
     + UnaryKernel<super::super::sqrt::SqrtKernelOp, E>
     + UnaryKernel<super::super::square::SquareKernelOp, E>