Fix custom reverse_forws for operators

Previously, nullptr used to be set as the derivative of a call in the reverse mode, if there was a custom reverse_forw function available. This issue was overlooked at first, since it doesn't cause any trouble, unless someone decides to use nested operators (such as expressions of the form `a[i] = x*x`). Fixes: #1070
vgvassilev · Sep 3, 2024 · 11443bf · 11443bf
1 parent c294ea5
commit 11443bf
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Showing 3 changed files with 50 additions and 2 deletions.
diff --git a/include/clad/Differentiator/STLBuiltins.h b/include/clad/Differentiator/STLBuiltins.h
@@ -206,7 +206,7 @@ template <typename T, typename U>
 void push_back_reverse_forw(::std::vector<T>* v, U val, ::std::vector<T>* d_v,
                             U d_val) {
   v->push_back(val);
-  d_v->push_back(0);
+  d_v->push_back(d_val);
 }
 
 template <typename T, typename U>

diff --git a/lib/Differentiator/ReverseModeVisitor.cpp b/lib/Differentiator/ReverseModeVisitor.cpp
@@ -2056,7 +2056,7 @@ Expr* getArraySizeExpr(const ArrayType* AT, ASTContext& context,
           utils::BuildMemberExpr(m_Sema, getCurrentScope(), callRes, "value");
       auto* resAdjoint =
           utils::BuildMemberExpr(m_Sema, getCurrentScope(), callRes, "adjoint");
-      return StmtDiff(resValue, nullptr, resAdjoint);
+      return StmtDiff(resValue, resAdjoint, resAdjoint);
     }
     if (utils::isNonConstReferenceType(returnType) ||
         returnType->isPointerType()) {

diff --git a/test/Gradient/STLCustomDerivatives.C b/test/Gradient/STLCustomDerivatives.C
@@ -103,17 +103,27 @@ double fn13(double u, double v) {
   return vec[0] + vec[1] + vec[2];
 }
 
+double fn14(double x, double y) {
+  std::vector<double> a;
+  a.push_back(x);
+  a.push_back(x);
+  a[1] = x*x;
+  return a[1];
+}
+
 int main() {
     double d_i, d_j;
     INIT_GRADIENT(fn10);
     INIT_GRADIENT(fn11);
     INIT_GRADIENT(fn12);
     INIT_GRADIENT(fn13);
+    INIT_GRADIENT(fn14);
 
     TEST_GRADIENT(fn10, /*numOfDerivativeArgs=*/2, 3, 5, &d_i, &d_j);  // CHECK-EXEC: {1.00, 1.00}
     TEST_GRADIENT(fn11, /*numOfDerivativeArgs=*/2, 3, 5, &d_i, &d_j);  // CHECK-EXEC: {2.00, 1.00}
     TEST_GRADIENT(fn12, /*numOfDerivativeArgs=*/2, 3, 5, &d_i, &d_j);  // CHECK-EXEC: {4.00, 2.00}
     TEST_GRADIENT(fn13, /*numOfDerivativeArgs=*/2, 3, 5, &d_i, &d_j);  // CHECK-EXEC: {3.00, 0.00}
+    TEST_GRADIENT(fn14, /*numOfDerivativeArgs=*/2, 3, 5, &d_i, &d_j);  // CHECK-EXEC: {6.00, 0.00}
 }
 
 // CHECK: void fn10_grad(double u, double v, double *_d_u, double *_d_v) {
@@ -381,3 +391,41 @@ int main() {
 // CHECK-NEXT:         {{.*}}constructor_pullback(&vec, count, u, allocator, &_d_vec, &_d_count, &*_d_u, &_d_allocator);
 // CHECK-NEXT:        *_d_u += _d_res;
 // CHECK-NEXT:     }
+
+// CHECK:      void fn14_grad(double x, double y, double *_d_x, double *_d_y) {
+// CHECK-NEXT:          std::vector<double> _d_a({});
+// CHECK-NEXT:          std::vector<double> a;
+// CHECK-NEXT:          double _t0 = x;
+// CHECK-NEXT:          std::vector<double> _t1 = a;
+// CHECK-NEXT:          {{.*}}push_back_reverse_forw(&a, x, &_d_a, *_d_x);
+// CHECK-NEXT:          double _t2 = x;
+// CHECK-NEXT:          std::vector<double> _t3 = a;
+// CHECK-NEXT:          {{.*}}push_back_reverse_forw(&a, x, &_d_a, *_d_x);
+// CHECK-NEXT:          std::vector<double> _t4 = a;
+// CHECK-NEXT:          clad::ValueAndAdjoint<double &, double &> _t5 = {{.*}}operator_subscript_reverse_forw(&a, 1, &_d_a, _r0);
+// CHECK-NEXT:          double _t6 = _t5.value;
+// CHECK-NEXT:          _t5.value = x * x;
+// CHECK-NEXT:          std::vector<double> _t7 = a;
+// CHECK-NEXT:          clad::ValueAndAdjoint<double &, double &> _t8 = {{.*}}operator_subscript_reverse_forw(&a, 1, &_d_a, _r1);
+// CHECK-NEXT:          {
+// CHECK-NEXT:              {{.*}} _r1 = 0;
+// CHECK-NEXT:              {{.*}}operator_subscript_pullback(&_t7, 1, 1, &_d_a, &_r1);
+// CHECK-NEXT:          }
+// CHECK-NEXT:          {
+// CHECK-NEXT:              _t5.value = _t6;
+// CHECK-NEXT:              double _r_d0 = _t5.adjoint;
+// CHECK-NEXT:              _t5.adjoint = 0;
+// CHECK-NEXT:              *_d_x += _r_d0 * x;
+// CHECK-NEXT:              *_d_x += x * _r_d0;
+// CHECK-NEXT:              {{.*}} _r0 = 0;
+// CHECK-NEXT:              {{.*}}operator_subscript_pullback(&_t4, 1, 0, &_d_a, &_r0);
+// CHECK-NEXT:          }
+// CHECK-NEXT:          {
+// CHECK-NEXT:              x = _t2;
+// CHECK-NEXT:              {{.*}}push_back_pullback(&_t3, _t2, &_d_a, &*_d_x);
+// CHECK-NEXT:          }
+// CHECK-NEXT:          {
+// CHECK-NEXT:              x = _t0;
+// CHECK-NEXT:              {{.*}}push_back_pullback(&_t1, _t0, &_d_a, &*_d_x);
+// CHECK-NEXT:          }
+// CHECK-NEXT:      }