Add basic support for std::tie and tuples in the fwd mode

include/clad/Differentiator/BuiltinDerivatives.h

@@ -30,6 +30,11 @@ template <typename T, typename U> struct ValueAndPushforward {
   }
 };
 
+template <typename T, typename U>
+ValueAndPushforward<T, U> make_value_and_pushforward(T value, U pushforward) {
+  return {value, pushforward};
+}
+
 template <typename T, typename U> struct ValueAndAdjoint {
   T value;
   U adjoint;

include/clad/Differentiator/STLBuiltins.h

@@ -1,8 +1,10 @@
 #ifndef CLAD_STL_BUILTINS_H
 #define CLAD_STL_BUILTINS_H
 
+#include <array>
 #include <clad/Differentiator/BuiltinDerivatives.h>
 #include <initializer_list>
+#include <tuple>
 #include <vector>
 
 namespace clad {
@@ -338,7 +340,87 @@ void constructor_pullback(::std::array<T, N>* a, const ::std::array<T, N>& arr,
     (*d_arr)[i] += (*d_a)[i];
 }
 
+template <typename... Args1, typename... Args2>
+clad::ValueAndPushforward<::std::tuple<Args1...>, ::std::tuple<Args1...>>
+operator_equal_pushforward(::std::tuple<Args1...>* tu,
+                           ::std::tuple<Args2...>&& in,
+                           ::std::tuple<Args1...>* d_tu,
+                           ::std::tuple<Args2...>&& d_in) noexcept {
+  ::std::tuple<Args1...> t1 = (*tu = in);
+  ::std::tuple<Args1...> t2 = (*d_tu = d_in);
+  return {t1, t2};
+}
+
 } // namespace class_functions
+
+namespace std {
+
+// Helper functions for selecting subtuples
+template <::std::size_t shift_amount, ::std::size_t... Is>
+constexpr auto shift_sequence(::std::index_sequence<Is...>) {
+  return ::std::index_sequence<shift_amount + Is...>{};
+}
+
+template <typename Tuple, ::std::size_t... Indices>
+auto select_tuple_elements(const Tuple& tpl,
+                           ::std::index_sequence<Indices...>) {
+  return ::std::make_tuple(::std::get<Indices>(tpl)...);
+}
+
+template <typename Tuple> auto first_half_tuple(const Tuple& tpl) {
+  // static_assert(::std::tuple_size<Tuple>::value % 2 == 0);
+  constexpr ::std::size_t half = ::std::tuple_size<Tuple>::value / 2;
+
+  constexpr ::std::make_index_sequence<half> first_half;
+  return select_tuple_elements(tpl, first_half);
+}
+
+template <typename Tuple> auto second_half_tuple(const Tuple& tpl) {
+  // static_assert(::std::tuple_size<Tuple>::value % 2 == 0);
+  constexpr ::std::size_t half = ::std::tuple_size<Tuple>::value / 2;
+
+  constexpr ::std::make_index_sequence<half> first_half;
+  constexpr auto second_half = shift_sequence<half>(first_half);
+  return select_tuple_elements(tpl, second_half);
+}
+
+template <typename Tuple, ::std::size_t... Indices>
+auto select_tuple_elements_tie(const Tuple& tpl,
+                               ::std::index_sequence<Indices...>) {
+  return ::std::tie(::std::get<Indices>(tpl)...);
+}
+
+template <typename Tuple> auto first_half_tuple_tie(const Tuple& tpl) {
+  // static_assert(::std::tuple_size<Tuple>::value % 2 == 0);
+  constexpr ::std::size_t half = ::std::tuple_size<Tuple>::value / 2;
+
+  constexpr ::std::make_index_sequence<half> first_half;
+  return select_tuple_elements_tie(tpl, first_half);
+}
+
+template <typename Tuple> auto second_half_tuple_tie(const Tuple& tpl) {
+  // static_assert(::std::tuple_size<Tuple>::value % 2 == 0);
+  constexpr ::std::size_t half = ::std::tuple_size<Tuple>::value / 2;
+
+  constexpr ::std::make_index_sequence<half> first_half;
+  constexpr auto second_half = shift_sequence<half>(first_half);
+  return select_tuple_elements_tie(tpl, second_half);
+}
+
+template <typename... Args> auto tie_pushforward(Args&&... args) noexcept {
+  ::std::tuple<Args&...> t = ::std::tie(args...);
+  return clad::make_value_and_pushforward(first_half_tuple_tie(t),
+                                          second_half_tuple_tie(t));
+}
+
+template <typename... Args> auto make_tuple_pushforward(Args... args) noexcept {
+  ::std::tuple<Args...> t = ::std::make_tuple(args...);
+  return clad::make_value_and_pushforward(first_half_tuple(t),
+                                          second_half_tuple(t));
+}
+
+} // namespace std
+
 } // namespace custom_derivatives
 } // namespace clad
 

test/ForwardMode/STLCustomDerivatives.C

@@ -1,4 +1,4 @@
-// RUN: %cladclang %s -std=c++14 -I%S/../../include -oSTLCustomDerivatives.out | %filecheck %s
+// RUN: %cladclang -std=c++17 %s -I%S/../../include -oSTLCustomDerivatives.out | %filecheck %s
 // RUN: ./STLCustomDerivatives.out | %filecheck_exec %s
 
 #include "clad/Differentiator/Differentiator.h"
@@ -7,6 +7,7 @@
 #include <array>
 #include <vector>
 #include <map>
+#include <tuple>
 
 #include "../TestUtils.h"
 #include "../PrintOverloads.h"
@@ -181,18 +182,48 @@ double fnArr2(double x) {
 //CHECK-NEXT:         return (_t0.pushforward * _t3 + _t2 * _t1.pushforward) * _t6 + _t5 * _t4.pushforward;
 //CHECK-NEXT:     }
 
+auto pack(double x) {
+    return std::make_tuple(x, 2*x, 3*x);
+}
+
+double fnTuple1(double x, double y) { 
+    double u, v = 288*x, w;
+
+    std::tie(u, v, w) = pack(x+y);
+
+    return v;
+} // = 2x + 2y
+
+//CHECK:      clad::ValueAndPushforward<tuple<double, double, double>, tuple<double, double, double> > pack_pushforward(double x, double _d_x);
+//CHECK:      double fnTuple1_darg0(double x, double y) {
+//CHECK-NEXT:          double _d_x = 1;
+//CHECK-NEXT:          double _d_y = 0;
+//CHECK-NEXT:          double _d_u, _d_v = 0 * x + 288 * _d_x, _d_w;
+//CHECK-NEXT:          double u, v = 288 * x, w;
+//CHECK-NEXT:          clad::ValueAndPushforward<tuple<double &, double &, double &>, tuple<double &, double &, double &> > _t0 = clad::custom_derivatives::std::tie_pushforward(u, v, w, _d_u, _d_v, _d_w);
+//CHECK-NEXT:          clad::ValueAndPushforward<tuple<double, double, double>, tuple<double, double, double> > _t1 = pack_pushforward(x + y, _d_x + _d_y);
+//CHECK-NEXT:          clad::ValueAndPushforward< ::std::tuple<double &, double &, double &>, ::std::tuple<double &, double &, double &> > _t2 = clad::custom_derivatives::class_functions::operator_equal_pushforward(&_t0.value, static_cast<std::tuple<double, double, double> &&>(_t1.value), &_t0.pushforward, static_cast<std::tuple<double, double, double> &&>(_t1.pushforward));
+//CHECK-NEXT:          return _d_v;
+//CHECK-NEXT:      }
+//CHECK:      clad::ValueAndPushforward<tuple<double, double, double>, tuple<double, double, double> > pack_pushforward(double x, double _d_x) {
+//CHECK-NEXT:          clad::ValueAndPushforward<tuple<double, double, double>, tuple<double, double, double> > _t0 = clad::custom_derivatives::std::make_tuple_pushforward(x, 2 * x, 3 * x, _d_x, 0 * x + 2 * _d_x, 0 * x + 3 * _d_x);
+//CHECK-NEXT:          return {_t0.value, _t0.pushforward};
+//CHECK-NEXT:      }
+
 int main() {
     INIT_DIFFERENTIATE(fnVec1, "u");
     INIT_DIFFERENTIATE(fnVec2, "u");
     INIT_DIFFERENTIATE(fnVec3, "u");
     INIT_DIFFERENTIATE(fnVec4, "u");
     INIT_DIFFERENTIATE(fnArr1, "x");
     INIT_DIFFERENTIATE(fnArr2, "x");
+    INIT_DIFFERENTIATE(fnTuple1, "x");
 
     TEST_DIFFERENTIATE(fnVec1, 3, 5); // CHECK-EXEC: {10.00}
     TEST_DIFFERENTIATE(fnVec2, 3, 5); // CHECK-EXEC: {5.00}
     TEST_DIFFERENTIATE(fnVec3, 3, 5); // CHECK-EXEC: {2.00}
     TEST_DIFFERENTIATE(fnVec4, 3, 5); // CHECK-EXEC: {30.00}
     TEST_DIFFERENTIATE(fnArr1, 3); // CHECK-EXEC: {3.00}
     TEST_DIFFERENTIATE(fnArr2, 3); // CHECK-EXEC: {108.00}
+    TEST_DIFFERENTIATE(fnTuple1, 3, 4); // CHECK-EXEC: {2.00}
 }

test/ForwardMode/UserDefinedTypes.C

@@ -1,4 +1,4 @@
-// RUN: %cladclang %s -I%S/../../include -oUserDefinedTypes.out | %filecheck %s
+// RUN: %cladclang -std=c++17 %s -I%S/../../include -oUserDefinedTypes.out | %filecheck %s
 // RUN: ./UserDefinedTypes.out | %filecheck_exec %s
 
 // XFAIL: asserts