Skip derivative creation of const vars and params

vgvassilev · Nov 3, 2024 · 583e80a · 583e80a
1 parent cddc21d
commit 583e80a
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diff --git a/lib/Differentiator/DiffPlanner.cpp b/lib/Differentiator/DiffPlanner.cpp
@@ -633,6 +633,9 @@ namespace clad {
   }
 
   bool DiffRequest::shouldHaveAdjoint(const VarDecl* VD) const {
+    if (VD->getType().isConstQualified())
+      return false;
+
     if (!EnableVariedAnalysis)
       return true;
 

diff --git a/lib/Differentiator/ReverseModeVisitor.cpp b/lib/Differentiator/ReverseModeVisitor.cpp
@@ -706,6 +706,8 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
           i == m_DiffReq->getNumParams() - 1)
         continue;
       auto VDDerivedType = param->getType();
+      if (VDDerivedType.isConstQualified())
+        continue;
       // We cannot initialize derived variable for pointer types because
       // we do not know the correct size.
       if (utils::isArrayOrPointerType(VDDerivedType))

diff --git a/test/Gradient/Assignments.C b/test/Gradient/Assignments.C
@@ -819,6 +819,34 @@ double f23(double x, double y) {
 //CHECK-NEXT:     }
 //CHECK-NEXT: }
 
+double constVal(double y, const double x) {
+  const double z = y;
+  y *= z;
+  return y * x;
+}
+
+//CHECK: void constVal_grad_0(double y, const double x, double *_d_y) {
+//CHECK-NEXT:    const double z = y;
+//CHECK-NEXT:    double _t0 = y;
+//CHECK-NEXT:    y *= z;
+//CHECK-NEXT:    *_d_y += 1 * x;
+//CHECK-NEXT:    {
+//CHECK-NEXT:        y = _t0;
+//CHECK-NEXT:        double _r_d0 = *_d_y;
+//CHECK-NEXT:        *_d_y = 0.;
+//CHECK-NEXT:        *_d_y += _r_d0 * z;
+//CHECK-NEXT:    }
+//CHECK-NEXT:}
+
+double constValInput(const double x) {
+  return x;
+}
+
+//CHECK: void constValInput_grad(const double x, double *_d_x) {
+//CHECK-NEXT:    *_d_x += 1;
+//CHECK-NEXT:}
+
+
 #define TEST(F, x, y)                                                          \
   {                                                                            \
     result[0] = 0;                                                             \
@@ -884,4 +912,14 @@ int main() {
   TEST(f21, 6, 4); // CHECK-EXEC: {1.00, 0.00}
   TEST(f22, 6, 4); // CHECK-EXEC: {0.00, 0.00}
   TEST(f23, 7, 5); // CHECK-EXEC: {1.00, 1.00}
+
+  auto const_test = clad::gradient(constVal, "y");
+  double const_test_result = 0;
+  const_test.execute(3, 4, &const_test_result);
+  printf("%.2f\n", const_test_result); // CHECK-EXEC: 12.00
+
+  auto const_test_input = clad::gradient(constValInput);
+  double const_test_input_result = 0;
+  const_test_input.execute(3, &const_test_input_result);
+  printf("%.2f\n", const_test_input_result); // CHECK-EXEC: 1.00
 }