feat: add silu activation function (#1706)

* feat: add silu activation function

* use silu/arg in grad

* update candle-nn

* use node

candle-metal-kernels/src/lib.rs

@@ -183,7 +183,7 @@ macro_rules! ops{
 pub mod unary {
     ops!(
         cos, sin, exp, sqr, sqrt, neg, log, gelu, abs, ceil, floor, relu, round, erf, gelu_erf,
-        tanh, recip
+        tanh, recip, silu
     );
 }
 pub mod binary {

candle-metal-kernels/src/tests.rs

@@ -231,6 +231,25 @@ fn gelu_f32() {
     assert_eq!(approx(results, 3), expected);
 }
 
+#[test]
+fn silu_f16() {
+    let v: Vec<f16> = [-10f32, -1.0, 0., 1., 2., 3., 10.0, 20.0]
+        .iter()
+        .map(|v| f16::from_f32(*v))
+        .collect();
+    let expected: Vec<f32> = vec![-0.0, -0.27, 0.0, 0.73, 1.76, 2.86, 10.0, 20.0];
+    let results = run(&v, unary::contiguous::silu::HALF);
+    assert_eq!(approx_f16(results, 2), expected);
+}
+
+#[test]
+fn silu_f32() {
+    let v: Vec<f32> = vec![-10f32, -1.0, 0., 1., 2., 3., 10.0, 20.0];
+    let expected: Vec<f32> = vec![-0.0, -0.269, 0.0, 0.731, 1.762, 2.858, 10.0, 20.0];
+    let results = run(&v, unary::contiguous::silu::FLOAT);
+    assert_eq!(approx(results, 3), expected);
+}
+
 #[test]
 fn binary_add_f32() {
     let left = vec![1.0f32, 2.0, 3.0];

candle-metal-kernels/src/unary.metal

@@ -64,6 +64,9 @@ template <typename T> METAL_FUNC T relu(T in){
     }
     return in;
 }
+template <typename T> METAL_FUNC T silu(T in){
+    return in / (static_cast<T>(1) + exp(-in));
+}
 
 #define UNARY(FN, TYPENAME, FN_NAME, FN_NAME_STRIDED) \
 kernel void FN_NAME( \
@@ -108,6 +111,7 @@ UNARY_OP(neg)
 UNARY_OP(exp)
 UNARY_OP(log)
 UNARY_OP(gelu)
+UNARY_OP(silu)
 UNARY_OP(abs)
 UNARY_OP(ceil)
 UNARY_OP(floor)
@@ -135,6 +139,7 @@ BFLOAT_UNARY_OP(neg)
 BFLOAT_UNARY_OP(exp)
 BFLOAT_UNARY_OP(log)
 BFLOAT_UNARY_OP(gelu)
+BFLOAT_UNARY_OP(silu)
 BFLOAT_UNARY_OP(abs)
 BFLOAT_UNARY_OP(ceil)
 BFLOAT_UNARY_OP(floor)