Implement gelu

src/gelu.js

@@ -0,0 +1,13 @@
+'use strict';
+
+import {erfKernel, unary} from './unary.js';
+
+/**
+ * Compute the gaussian error linear unit function (GELU) of the input tensor.
+ * The calculation follows the expression 0.5 * x * (1 + erf(x / sqrt(2))).
+ * @param {Tensor} input
+ * @return {Tensor}
+ */
+export function gelu(input) {
+  return unary(input, (x) => 0.5 * x * (1 + erfKernel(x / Math.sqrt(2))));
+}

src/unary.js

@@ -18,19 +18,7 @@ export function unary(input, unaryFunc) {
   return output;
 }
 
-export const abs = (input) => unary(input, Math.abs);
-export const ceil = (input) => unary(input, Math.ceil);
-export const cos = (input) => unary(input, Math.cos);
-export const exp = (input) => unary(input, Math.exp);
-export const floor = (input) => unary(input, Math.floor);
-export const log = (input) => unary(input, Math.log);
-export const neg = (input) => unary(input, (x) => -1 * x);
-export const sin = (input) => unary(input, Math.sin);
-export const tan = (input) => unary(input, Math.tan);
-export const copy = (input) => unary(input, (x) => x);
-export const reciprocal = (input) => unary(input, (x) => 1 / x);
-export const sqrt = (input) => unary(input, Math.sqrt);
-export const erf = (input) => unary(input, (x) => {
+export function erfKernel(x) {
   // reference 1: https://en.wikipedia.org/wiki/Error_function
   // reference 2: https://github.com/tensorflow/tfjs/blob/master/tfjs-backend-cpu/src/kernels/Erf.ts
   const a1 = 0.254829592;
@@ -46,4 +34,18 @@ export const erf = (input) => unary(input, (x) => {
       (1.0 -
           (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t *
           Math.exp(-v * v));
-});
+}
+
+export const abs = (input) => unary(input, Math.abs);
+export const ceil = (input) => unary(input, Math.ceil);
+export const cos = (input) => unary(input, Math.cos);
+export const exp = (input) => unary(input, Math.exp);
+export const floor = (input) => unary(input, Math.floor);
+export const log = (input) => unary(input, Math.log);
+export const neg = (input) => unary(input, (x) => -1 * x);
+export const sin = (input) => unary(input, Math.sin);
+export const tan = (input) => unary(input, Math.tan);
+export const copy = (input) => unary(input, (x) => x);
+export const reciprocal = (input) => unary(input, (x) => 1 / x);
+export const sqrt = (input) => unary(input, Math.sqrt);
+export const erf = (input) => unary(input, erfKernel);

test/gelu_test.js

@@ -0,0 +1,20 @@
+'use strict';
+
+import {gelu} from '../src/gelu.js';
+import {Tensor} from '../src/lib/tensor.js';
+import * as utils from './utils.js';
+
+describe('test gelu', function() {
+  function testGelu(inputShape, inputValue, expected) {
+    const inputTensor = new Tensor(inputShape, inputValue);
+    const outputTensor = gelu(inputTensor);
+    utils.checkValue(outputTensor, expected);
+  }
+
+  it('gelu', function() {
+    // Refer to ONNX gelu_default test:
+    // https://github.com/onnx/onnx/blob/main/docs/Operators.md#gelu
+    testGelu([3], [-1, 0, 1], [-0.15865526383236372, 0, 0.8413447361676363]);
+    testGelu([1, 1, 1, 3], [-1, 0, 1], [-0.15865526383236372, 0, 0.8413447361676363]);
+  });
+});