[libc++][PSTL] Implement std::generate{,_n}

[ldionne]

libcxx/include/CMakeLists.txt

85

Don't forget to update the paper list.

libcxx/include/__algorithm/pstl_generate.h

2

Missing updates to the customization point list.

libcxx/include/algorithm

1818

Missing synopsis update. Did we forget to update it for the past several patches? I get a feeling that we did.

[philnik]

Address comments

libcxx/docs/Status/PSTLPaper.csv

 | `[alg.fill] <https://wg21.link/alg.fill>`_,std::fill_n,Nikolas Klauser,|Complete|
 | `[alg.find] <https://wg21.link/alg.find>`_,std::find,Nikolas Klauser,|Complete|
 | `[alg.find.end] <https://wg21.link/alg.find.end>`_,std::find_end,Nikolas Klauser,|Not Started|
 | `[alg.find.first.of] <https://wg21.link/alg.find.first.of>`_,std::find_first_of,Nikolas Klauser,|Not Started|
 | `[alg.find] <https://wg21.link/alg.find>`_,std::find_if,Nikolas Klauser,|Complete|
 | `[alg.find] <https://wg21.link/alg.find>`_,std::find_if_not,Nikolas Klauser,|Complete|
 | `[alg.foreach] <https://wg21.link/alg.foreach>`_,std::for_each,Nikolas Klauser,|Complete|
 | `[alg.foreach] <https://wg21.link/alg.foreach>`_,std::for_each_n,Nikolas Klauser,|Complete|
-| `[alg.generate] <https://wg21.link/alg.generate>`_,std::generate,Nikolas Klauser,|In Progress|
-| `[alg.generate] <https://wg21.link/alg.generate>`_,std::generate_n,Nikolas Klauser,|In Progress|
+| `[alg.generate] <https://wg21.link/alg.generate>`_,std::generate,Nikolas Klauser,|Complete|
+| `[alg.generate] <https://wg21.link/alg.generate>`_,std::generate_n,Nikolas Klauser,|Complete|
 | `[alg.set.operations] <https://wg21.link/alg.set.operations>`_,std::includes,Nikolas Klauser,|Not Started|
 | `[alg.inclusive.scan] <https://wg21.link/alg.inclusive.scan>`_,std::inclusive_scan,Nikolas Klauser,|Not Started|
 | `[alg.merge] <https://wg21.link/alg.merge>`_,std::inplace_merge,Nikolas Klauser,|Not Started|
 | `[alg.heap.operations] <https://wg21.link/alg.heap.operations>`_,std::is_heap,Nikolas Klauser,|Not Started|
 | `[alg.heap.operations] <https://wg21.link/alg.heap.operations>`_,std::is_heap_until,Nikolas Klauser,|Not Started|
 | `[alg.partitions] <https://wg21.link/alg.partitions>`_,std::is_partitioned,Nikolas Klauser,|Not Started|
 | `[alg.sort] <https://wg21.link/alg.sort>`_,std::is_sorted,Nikolas Klauser,|Not Started|
 | `[alg.sort] <https://wg21.link/alg.sort>`_,std::is_sorted_until,Nikolas Klauser,|Not Started|

libcxx/include/CMakeLists.txt

set(files
   __algorithm/pstl_backends/cpu_backends/backend.h
   __algorithm/pstl_backends/cpu_backends/fill.h
   __algorithm/pstl_backends/cpu_backends/find_if.h
   __algorithm/pstl_backends/cpu_backends/for_each.h
   __algorithm/pstl_backends/cpu_backends/merge.h
   __algorithm/pstl_backends/cpu_backends/serial.h
   __algorithm/pstl_backends/cpu_backends/stable_sort.h
   __algorithm/pstl_backends/cpu_backends/thread.h
   __algorithm/pstl_backends/cpu_backends/transform.h
   __algorithm/pstl_backends/cpu_backends/transform_reduce.h
   __algorithm/pstl_copy.h
   __algorithm/pstl_count.h
   __algorithm/pstl_fill.h
   __algorithm/pstl_find.h
   __algorithm/pstl_for_each.h
   __algorithm/pstl_frontend_dispatch.h
+  __algorithm/pstl_generate.h
   __algorithm/pstl_merge.h
   __algorithm/pstl_replace.h
   __algorithm/pstl_stable_sort.h
   __algorithm/pstl_transform.h
   __algorithm/push_heap.h
   __algorithm/ranges_adjacent_find.h
   __algorithm/ranges_all_of.h
   __algorithm/ranges_any_of.h

libcxx/include/__algorithm/pstl_backend.h

implemented, all the algorithms will eventually forward to the basis algorithms listed above:
   _Iterator __pstl_find_if_not(_Backend, _Iterator __first, _Iterator __last, _Predicate __pred);
 
   template <class _ExecutionPolicy, class _Iterator, class _Tp>
   void __pstl_fill(_Backend, _Iterator __first, _Iterator __last, const _Tp& __value);
 
   template <class _ExecutionPolicy, class _Iterator, class _SizeT, class _Tp>
   void __pstl_fill_n(_Backend, _Iterator __first, _SizeT __n, const _Tp& __value);
 
+  template <class _ExecutionPolicy, class _Iterator, class _Generator>
+  void __pstl_generate(_Backend, _Iterator __first, _Iterator __last, _Generator __gen);
+
+  template <class _ExecutionPolicy, class _Iterator, class _Size, class _Generator>
+  void __pstl_generator_n(_Backend, _Iterator __first, _Size __n, _Generator __gen);
+
   template <class _ExecutionPolicy, class _terator1, class _Iterator2, class _OutIterator, class _Comp>
   _OutIterator __pstl_merge(_Backend,
                             _Iterator1 __first1,
                             _Iterator1 __last1,
                             _Iterator2 __first2,
                             _Iterator2 __last2,
                             _OutIterator __result,
                             _Comp __comp);

libcxx/include/__algorithm/pstl_generate.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_PSTL_GENERATE_H
+#define _LIBCPP___ALGORITHM_PSTL_GENERATE_H
+
+#include <__algorithm/pstl_backend.h>
+#include <__algorithm/pstl_for_each.h>
+#include <__algorithm/pstl_frontend_dispatch.h>
+#include <__config>
+#include <__iterator/cpp17_iterator_concepts.h>
+#include <__type_traits/is_execution_policy.h>
+#include <__type_traits/remove_cvref.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class>
+void __pstl_generate();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+generate(_ExecutionPolicy&& __policy, _ForwardIterator __first, _ForwardIterator __last, _Generator __gen) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator);
+  std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate),
+      [&__policy](_ForwardIterator __g_first, _ForwardIterator __g_last, _Generator __g_gen) {
+        std::for_each(
+            __policy, std::move(__g_first), std::move(__g_last), [&](__iter_reference<_ForwardIterator> __element) {
+              __element = __g_gen();
+            });
+      },
+      std::move(__first),
+      std::move(__last),
+      std::move(__gen));
+}
+
+template <class>
+void __pstl_generate_n();
+
+template <class _ExecutionPolicy,
+          class _ForwardIterator,
+          class _Size,
+          class _Generator,
+          class _RawPolicy                                    = __remove_cvref_t<_ExecutionPolicy>,
+          enable_if_t<is_execution_policy_v<_RawPolicy>, int> = 0>
+_LIBCPP_HIDE_FROM_ABI void
+generate_n(_ExecutionPolicy&& __policy, _ForwardIterator __first, _Size __n, _Generator __gen) {
+  _LIBCPP_REQUIRE_CPP17_FORWARD_ITERATOR(_ForwardIterator);
+  std::__pstl_frontend_dispatch(
+      _LIBCPP_PSTL_CUSTOMIZATION_POINT(__pstl_generate_n),
+      [&__policy](_ForwardIterator __g_first, _Size __g_n, _Generator __g_gen) {
+        std::for_each_n(__policy, std::move(__g_first), __g_n, [&](__iter_reference<_ForwardIterator> __element) {
+          __element = __g_gen();
+        });
+      },
+      std::move(__first),
+      __n,
+      std::move(__gen));
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+#endif // _LIBCPP___ALGORITHM_PSTL_GENERATE_H

libcxx/include/algorithm

template<input_range R, class Proj = identity,
 
   template<class T, output_iterator<const T&> O>
     constexpr O ranges::fill_n(O first, iter_difference_t<O> n, const T& value);            // since C++20
 
   template<input_or_output_iterator O, sentinel_for<O> S, copy_constructible F>
     requires invocable<F&> && indirectly_writable<O, invoke_result_t<F&>>
     constexpr O generate(O first, S last, F gen);                                           // since C++20
 
+  template<class ExecutionPolicy, class ForwardIterator, class Generator>
+    void generate(ExecutionPolicy&& exec,
+                  ForwardIterator first, ForwardIterator last,
+                  Generator gen);                                                           // since C++17
+
   template<class R, copy_constructible F>
     requires invocable<F&> && output_range<R, invoke_result_t<F&>>
     constexpr borrowed_iterator_t<R> generate(R&& r, F gen);                                // since C++20
 
   template<input_or_output_iterator O, copy_constructible F>
     requires invocable<F&> && indirectly_writable<O, invoke_result_t<F&>>
     constexpr O generate_n(O first, iter_difference_t<O> n, F gen);                         // since C++20
 
+  template<class ExecutionPolicy, class ForwardIterator, class Size, class Generator>
+    ForwardIterator generate_n(ExecutionPolicy&& exec,
+                               ForwardIterator first, Size n, Generator gen);               // since C++17
+
  template<input_iterator I1, sentinel_for<I1> S1, input_iterator I2, sentinel_for<I2> S2,
           class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
    requires indirectly_comparable<I1, I2, Pred, Proj1, Proj2>
    constexpr bool ranges::equal(I1 first1, S1 last1, I2 first2, S2 last2,
                                 Pred pred = {},
                                 Proj1 proj1 = {}, Proj2 proj2 = {});                        // since C++20
 
  template<input_range R1, input_range R2, class Pred = ranges::equal_to,

 #include <__algorithm/pop_heap.h>
 #include <__algorithm/prev_permutation.h>
 #include <__algorithm/pstl_any_all_none_of.h>
 #include <__algorithm/pstl_copy.h>
 #include <__algorithm/pstl_count.h>
 #include <__algorithm/pstl_fill.h>
 #include <__algorithm/pstl_find.h>
 #include <__algorithm/pstl_for_each.h>
+#include <__algorithm/pstl_generate.h>
 #include <__algorithm/pstl_merge.h>
 #include <__algorithm/pstl_replace.h>
 #include <__algorithm/pstl_stable_sort.h>
 #include <__algorithm/pstl_transform.h>
 #include <__algorithm/push_heap.h>
 #include <__algorithm/ranges_adjacent_find.h>
 #include <__algorithm/ranges_all_of.h>
 #include <__algorithm/ranges_any_of.h>

libcxx/test/libcxx/algorithms/pstl.robust_against_customization_points_not_working.pass.cpp

 template <class, class ForwardIterator, class Pred>
 typename std::iterator_traits<ForwardIterator>::difference_type
 __pstl_count_if(TestBackend, ForwardIterator, ForwardIterator, Pred) {
   assert(!pstl_count_if_called);
   pstl_count_if_called = true;
   return 0;
 }
 
+bool pstl_generate_called = false;
+
+template <class, class ForwardIterator, class Gen>
+void __pstl_generate(TestBackend, ForwardIterator, ForwardIterator, Gen) {
+  assert(!pstl_generate_called);
+  pstl_generate_called = true;
+}
+
+bool pstl_generate_n_called = false;
+
+template <class, class ForwardIterator, class Size, class Gen>
+void __pstl_generate_n(TestBackend, Size, ForwardIterator, Gen) {
+  assert(!pstl_generate_n_called);
+  pstl_generate_n_called = true;
+}
+
 bool pstl_none_of_called = false;
 
 template <class, class ForwardIterator, class Pred>
 bool __pstl_none_of(TestBackend, ForwardIterator, ForwardIterator, Pred) {
   assert(!pstl_none_of_called);
   pstl_none_of_called = true;
   return true;
 }
int main(int, char**) {
   (void)std::find_if(TestPolicy{}, std::begin(a), std::end(a), pred);
   assert(std::pstl_find_if_called);
   (void)std::find_if_not(TestPolicy{}, std::begin(a), std::end(a), pred);
   assert(std::pstl_find_if_not_called);
   (void)std::for_each(TestPolicy{}, std::begin(a), std::end(a), pred);
   assert(std::pstl_for_each_called);
   (void)std::for_each_n(TestPolicy{}, std::begin(a), std::size(a), pred);
   assert(std::pstl_for_each_n_called);
+  (void)std::generate(TestPolicy{}, std::begin(a), std::end(a), pred);
+  assert(std::pstl_generate_called);
+  (void)std::generate_n(TestPolicy{}, std::begin(a), std::size(a), pred);
+  assert(std::pstl_generate_n_called);
   (void)std::replace(TestPolicy{}, std::begin(a), std::end(a), 0, 0);
   assert(std::pstl_replace_called);
   (void)std::replace_if(TestPolicy{}, std::begin(a), std::end(a), pred, 0);
   assert(std::pstl_replace_if_called);
   (void)std::replace_copy(TestPolicy{}, std::begin(a), std::end(a), std::begin(a), 0, 0);
   assert(std::pstl_replace_copy_called);
   (void)std::replace_copy_if(TestPolicy{}, std::begin(a), std::end(a), std::begin(a), pred, 0);
   assert(std::pstl_replace_copy_if_called);

libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/pstl.generate.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// UNSUPPORTED: libcpp-has-no-incomplete-pstl
+
+// template<class ExecutionPolicy, class ForwardIterator, class Generator>
+//   void generate(ExecutionPolicy&& exec,
+//                 ForwardIterator first, ForwardIterator last,
+//                 Generator gen);
+
+#include <algorithm>
+#include <cassert>
+#include <vector>
+
+#include "test_iterators.h"
+#include "test_execution_policies.h"
+#include "type_algorithms.h"
+
+template <class Iter>
+struct Test {
+  template <class ExecutionPolicy>
+  void operator()(ExecutionPolicy&& policy) {
+    { // simple test
+      int a[10];
+      std::generate(policy, Iter(std::begin(a)), Iter(std::end(a)), []() { return 1; });
+      assert(std::all_of(std::begin(a), std::end(a), [](int i) { return i == 1; }));
+    }
+    { // empty range works
+      int a[10] {3};
+      std::generate(policy, Iter(std::begin(a)), Iter(std::begin(a)), []() { return 1; });
+      assert(a[0] == 3);
+    }
+    { // single-element range works
+      int a[] {3};
+      std::generate(policy, Iter(std::begin(a)), Iter(std::end(a)), []() { return 5; });
+      assert(a[0] == 5);
+    }
+    { // large range works
+      std::vector<int> vec(150, 4);
+      std::generate(policy, Iter(std::data(vec)), Iter(std::data(vec) + std::size(vec)), []() { return 5; });
+      assert(std::all_of(std::begin(vec), std::end(vec), [](int i) { return i == 5; }));
+    }
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, TestIteratorWithPolicies<Test>{});
+
+  return 0;
+}

libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/pstl.generate_n.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// UNSUPPORTED: libcpp-has-no-incomplete-pstl
+
+// template<class ExecutionPolicy, class ForwardIterator, class Size, class Generator>
+//   ForwardIterator generate_n(ExecutionPolicy&& exec,
+//                              ForwardIterator first, Size n, Generator gen);
+
+#include <algorithm>
+#include <cassert>
+#include <vector>
+
+#include "test_iterators.h"
+#include "test_execution_policies.h"
+#include "type_algorithms.h"
+
+template <class Iter>
+struct Test {
+  template <class ExecutionPolicy>
+  void operator()(ExecutionPolicy&& policy) {
+    { // simple test
+      int a[10];
+      std::generate_n(policy, Iter(std::begin(a)), std::size(a), []() { return 1; });
+      assert(std::all_of(std::begin(a), std::end(a), [](int i) { return i == 1; }));
+    }
+    { // empty range works
+      int a[10] {3};
+      std::generate_n(policy, Iter(std::begin(a)), 0, []() { return 1; });
+      assert(a[0] == 3);
+    }
+    { // single-element range works
+      int a[] {3};
+      std::generate_n(policy, Iter(std::begin(a)), std::size(a), []() { return 5; });
+      assert(a[0] == 5);
+    }
+    { // large range works
+      std::vector<int> vec(150, 4);
+      std::generate_n(policy, Iter(std::data(vec)), std::size(vec), []() { return 5; });
+      assert(std::all_of(std::begin(vec), std::end(vec), [](int i) { return i == 5; }));
+    }
+  }
+};
+
+int main(int, char**) {
+  types::for_each(types::forward_iterator_list<int*>{}, TestIteratorWithPolicies<Test>{});
+
+  return 0;
+}