add ci workflow

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  cmake:
+    name: ${{ matrix.os }} / ${{ matrix.preset }}
+    runs-on: ${{ matrix.os }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        preset: [debug, release]
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v7
+
+      - name: Configure
+        run: cmake --preset ${{ matrix.preset }}
+
+      - name: Build
+        run: cmake --build --preset ${{ matrix.preset }}
+
+      - name: Test
+        run: ctest --preset ${{ matrix.preset }}

src/value.c

@@ -257,6 +257,7 @@ bool mg_backward(mg_graph* g, mg_value* out) {
                 v->left->grad += v->right->data *
                                  powf(v->left->data, v->right->data - 1.0f) *
                                  v->grad;
+                v->right->grad += v->data * logf(v->left->data) * v->grad;
                 break;
             case MG_OP_RELU:
                 v->left->grad += (v->data > 0.0) * v->grad;

test/test.c

@@ -111,7 +111,7 @@ static void test_pow(void) {
 
     expect_close("pow data", mg_data(out), 64.0f);
     expect_close("pow base grad", mg_grad(base), 48.0f);
-    expect_close("pow exponent grad", mg_grad(exponent), 0.0f);
+    expect_close("pow exponent grad", mg_grad(exponent), 64.0f * logf(4.0f));
 
     mg_graph_free(g);
 }