From 7289d0b4545935655bf4695f6599a88d0baaaf69 Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <johan511@rostam1.rostam.cct.lsu.edu>
Date: Sun, 16 Jul 2023 07:21:14 -0500
Subject: [PATCH 1/6] unseq find

Signed-off-by: Hari Hara Naveen S <johan511@rostam1.rostam.cct.lsu.edu>
---
 .../hpx/parallel/algorithms/detail/find.hpp   |  3 +-
 .../include/hpx/parallel/util/loop.hpp        | 41 +++++++++++++++++--
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
index 649e386386e9..30db28d9ac45 100644
--- a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
@@ -34,8 +34,7 @@ namespace hpx::parallel::detail {
             sequential_find_t<ExPolicy>, Iterator first, Sentinel last,
             T const& value, Proj proj = Proj())
         {
-            return util::loop_pred<
-                std::decay_t<hpx::execution::sequenced_policy>>(
+            return util::loop_pred<ExPolicy>(
                 first, last, [&value, &proj](auto const& curr) {
                     return HPX_INVOKE(proj, *curr) == value;
                 });
diff --git a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
index b3207bc980e7..579cc0eafb81 100644
--- a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
@@ -15,6 +15,7 @@
 #include <hpx/functional/detail/tag_fallback_invoke.hpp>
 #include <hpx/functional/invoke_result.hpp>
 #include <hpx/iterator_support/traits/is_iterator.hpp>
+#include <hpx/parallel/unseq/simd_helpers.hpp>
 #include <hpx/type_support/identity.hpp>
 
 #include <algorithm>
@@ -149,11 +150,12 @@ namespace hpx::parallel::util {
 
     ///////////////////////////////////////////////////////////////////////////
     namespace detail {
-
+        template <typename Iterator, typename ExPolicy>
+        struct loop_pred;
         // Helper class to repeatedly call a function starting from a given
         // iterator position till the predicate returns true.
         template <typename Iterator>
-        struct loop_pred
+        struct loop_pred<Iterator, void>
         {
             ///////////////////////////////////////////////////////////////////
             template <typename Begin, typename End, typename Pred>
@@ -170,6 +172,39 @@ namespace hpx::parallel::util {
         };
     }    // namespace detail
 
+    ///////////////////////////////////////////////////////////////////////////
+    namespace detail {
+
+        // Helper class to repeatedly call a function starting from a given
+        // iterator position till the predicate returns true.
+        template <typename Iterator, typename ExPolicy>
+        struct loop_pred
+        {
+            ///////////////////////////////////////////////////////////////////
+            template <typename Begin, typename End, typename Pred>
+            HPX_HOST_DEVICE HPX_FORCEINLINE static constexpr Begin call(
+                Begin it, End end, Pred&& pred)
+            {
+                if constexpr (hpx::is_unsequenced_execution_policy_v<
+                                  ExPolicy> &&
+                    hpx::traits::is_random_access_iterator_v<Begin>)
+                {
+                    return unseq_first_n(
+                        it, std::distance(it, end), HPX_FORWARD(Pred, pred));
+                }
+                else
+                {
+                    for (/**/; it != end; ++it)
+                    {
+                        if (HPX_INVOKE(pred, it))
+                            return it;
+                    }
+                    return it;
+                }
+            }
+        };
+    }    // namespace detail
+
     template <typename ExPolicy>
     struct loop_pred_t final
       : hpx::functional::detail::tag_fallback<loop_pred_t<ExPolicy>>
@@ -180,7 +215,7 @@ namespace hpx::parallel::util {
         tag_fallback_invoke(hpx::parallel::util::loop_pred_t<ExPolicy>,
             Begin begin, End end, Pred&& pred)
         {
-            return detail::loop_pred<Begin>::call(
+            return detail::loop_pred<Begin, ExPolicy>::call(
                 begin, end, HPX_FORWARD(Pred, pred));
         }
     };

From 09b39e6c99cff3c70b6a6d498594f32c0f448b68 Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <johan511@rostam1.rostam.cct.lsu.edu>
Date: Sun, 16 Jul 2023 08:55:40 -0500
Subject: [PATCH 2/6] predicate parameter in simd-helpers first take iterators

Signed-off-by: Hari Hara Naveen S <johan511@rostam1.rostam.cct.lsu.edu>

changing test according to change made to helper

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>
---
 .../include/hpx/parallel/unseq/simd_helpers.hpp    | 14 +++++++-------
 .../unit/algorithms/util/test_simd_helpers.cpp     |  4 ++--
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
index 4ecc66cfdcfc..4e2dd5131810 100644
--- a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
@@ -42,7 +42,7 @@ namespace hpx::parallel::util {
         HPX_PRAGMA_VECTOR_UNALIGNED HPX_PRAGMA_SIMD_EARLYEXIT
         for (; i < n; ++i)
         {
-            if (f(*(first + i)))
+            if (f(first + i))
             {
                 break;
             }
@@ -64,7 +64,7 @@ namespace hpx::parallel::util {
             HPX_PRAGMA_VECTOR_UNALIGNED HPX_VECTOR_REDUCTION(| : found_flag)
             for (IterDiff j = i; j < i + num_blocks; ++j)
             {
-                std::int32_t const t = f(*(first + j));
+                std::int32_t const t = f(first + j);
                 simd_lane[j - i] = t;
                 found_flag |= t;
             }
@@ -88,7 +88,7 @@ namespace hpx::parallel::util {
         //Keep remainder scalar
         while (i != n)
         {
-            if (f(*(first + i)))
+            if (f(first + i))
             {
                 break;
             }
@@ -108,7 +108,7 @@ namespace hpx::parallel::util {
         // clang-format off
         HPX_PRAGMA_VECTOR_UNALIGNED HPX_PRAGMA_SIMD_EARLYEXIT
         for (; i < n; ++i)
-            if (f(*(first1 + i), *(first2 + i)))
+            if (f(first1 + i, first2 + i))
                 break;
         // clang-format on
 
@@ -129,8 +129,8 @@ namespace hpx::parallel::util {
             HPX_PRAGMA_VECTOR_UNALIGNED HPX_VECTOR_REDUCTION(| : found_flag)
             for (i = 0; i < num_blocks; ++i)
             {
-                IterDiff const t = f(*(first1 + outer_loop_ind + i),
-                    *(first2 + outer_loop_ind + i));
+                IterDiff const t = f(first1 + outer_loop_ind + i,
+                    first2 + outer_loop_ind + i);
                 simd_lane[i] = t;
                 found_flag |= t;
             }
@@ -152,7 +152,7 @@ namespace hpx::parallel::util {
 
         //Keep remainder scalar
         for (; outer_loop_ind != n; ++outer_loop_ind)
-            if (f(*(first1 + outer_loop_ind), *(first2 + outer_loop_ind)))
+            if (f(first1 + outer_loop_ind, first2 + outer_loop_ind))
                 break;
 
         return std::make_pair(first1 + outer_loop_ind, first2 + outer_loop_ind);
diff --git a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
index 9fc98de2af61..932867e03a9d 100644
--- a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
+++ b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
@@ -36,7 +36,7 @@ void test_unseq_first_n1_dispatch2(std::size_t length, std::size_t first_index)
         i++;
     });
 
-    auto f = [](T t) { return t; };
+    auto f = [](auto t) { return *t; };
 
     auto iter_test = hpx::parallel::util::unseq_first_n(
         v.begin(), static_cast<T>(length), f);
@@ -80,7 +80,7 @@ void test_unseq_first_n2_dispatch2(std::size_t length, std::size_t first_index)
         idx++;
     }
 
-    auto f = [](T t1, T t2) { return t1 && t2; };
+    auto f = [](auto t1, auto t2) { return *t1 && *t2; };
 
     auto iter_pair_test = hpx::parallel::util::unseq2_first_n(
         v1.begin(), v2.begin(), static_cast<T>(length), f);

From c6a69325cb0e77582886100ae4af90ff53e8ed8a Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <harihara.sn@gmail.com>
Date: Tue, 18 Jul 2023 04:36:17 -0500
Subject: [PATCH 3/6] adding par_unseq to find

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>

unseq

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>
---
 .../hpx/parallel/algorithms/detail/find.hpp   |  3 ++
 .../include/hpx/parallel/util/loop.hpp        | 49 ++++++++++++-------
 2 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
index 30db28d9ac45..8d80fe055f3c 100644
--- a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
@@ -45,6 +45,7 @@ namespace hpx::parallel::detail {
             std::size_t base_idx, FwdIter part_begin, std::size_t part_count,
             Token& tok, T const& val, Proj&& proj)
         {
+            // TODO
             util::loop_idx_n<ExPolicy>(base_idx, part_begin, part_count, tok,
                 [&val, &proj, &tok](auto& v, std::size_t i) -> void {
                     if (HPX_INVOKE(proj, v) == val)
@@ -101,6 +102,7 @@ namespace hpx::parallel::detail {
             sequential_find_if_t<ExPolicy>, FwdIter part_begin,
             std::size_t part_count, Token& tok, F&& op, Proj&& proj)
         {
+            // TODO
             util::loop_n<std::decay_t<ExPolicy>>(part_begin, part_count, tok,
                 [&op, &tok, &proj](auto const& curr) {
                     if (HPX_INVOKE(op, HPX_INVOKE(proj, *curr)))
@@ -116,6 +118,7 @@ namespace hpx::parallel::detail {
             FwdIter part_begin, std::size_t part_count, Token& tok, F&& f,
             Proj&& proj)
         {
+            // TODO
             util::loop_idx_n<ExPolicy>(base_idx, part_begin, part_count, tok,
                 [&f, &proj, &tok](auto& v, std::size_t i) -> void {
                     if (HPX_INVOKE(f, HPX_INVOKE(proj, v)))
diff --git a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
index 579cc0eafb81..4018c05ea12c 100644
--- a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
@@ -185,22 +185,12 @@ namespace hpx::parallel::util {
             HPX_HOST_DEVICE HPX_FORCEINLINE static constexpr Begin call(
                 Begin it, End end, Pred&& pred)
             {
-                if constexpr (hpx::is_unsequenced_execution_policy_v<
-                                  ExPolicy> &&
-                    hpx::traits::is_random_access_iterator_v<Begin>)
-                {
-                    return unseq_first_n(
-                        it, std::distance(it, end), HPX_FORWARD(Pred, pred));
-                }
-                else
+                for (/**/; it != end; ++it)
                 {
-                    for (/**/; it != end; ++it)
-                    {
-                        if (HPX_INVOKE(pred, it))
-                            return it;
-                    }
-                    return it;
+                    if (HPX_INVOKE(pred, it))
+                        return it;
                 }
+                return it;
             }
         };
     }    // namespace detail
@@ -220,6 +210,27 @@ namespace hpx::parallel::util {
         }
     };
 
+    template <typename Begin, typename End, typename Pred,
+        HPX_CONCEPT_REQUIRES_(hpx::traits::is_random_access_iterator_v<Begin>)>
+    HPX_HOST_DEVICE HPX_FORCEINLINE Begin tag_invoke(
+        hpx::parallel::util::loop_pred_t<hpx::execution::unsequenced_policy>,
+        Begin HPX_RESTRICT begin, End HPX_RESTRICT end, Pred&& pred)
+    {
+        return unseq_first_n(
+            begin, std::distance(begin, end), HPX_FORWARD(Pred, pred));
+    }
+
+    template <typename Begin, typename End, typename Pred,
+        HPX_CONCEPT_REQUIRES_(hpx::traits::is_random_access_iterator_v<Begin>)>
+    HPX_HOST_DEVICE HPX_FORCEINLINE Begin tag_invoke(
+        hpx::parallel::util::loop_pred_t<
+            hpx::execution::unsequenced_task_policy>,
+        Begin HPX_RESTRICT begin, End HPX_RESTRICT end, Pred&& pred)
+    {
+        return unseq_first_n(
+            begin, std::distance(begin, end), HPX_FORWARD(Pred, pred));
+    }
+
 #if !defined(HPX_COMPUTE_DEVICE_CODE)
     template <typename ExPolicy>
     inline constexpr loop_pred_t<ExPolicy> loop_pred = loop_pred_t<ExPolicy>{};
@@ -1161,7 +1172,7 @@ namespace hpx::parallel::util {
 
         // Helper class to repeatedly call a function a given number of times
         // starting from a given iterator position.
-        template <typename IterCat>
+        template <typename IterCat, typename Dummy = void>
         struct loop_idx_n
         {
             ///////////////////////////////////////////////////////////////////
@@ -1199,8 +1210,8 @@ namespace hpx::parallel::util {
             }
         };
 
-        template <>
-        struct loop_idx_n<std::random_access_iterator_tag>
+        template <typename ExPolicy>
+        struct loop_idx_n<std::random_access_iterator_tag, ExPolicy>
         {
             ///////////////////////////////////////////////////////////////////
             // handle sequences of non-futures
@@ -1268,7 +1279,7 @@ namespace hpx::parallel::util {
             std::size_t base_idx, Iter it, std::size_t count, F&& f)
         {
             using cat = typename std::iterator_traits<Iter>::iterator_category;
-            return detail::loop_idx_n<cat>::call(
+            return detail::loop_idx_n<cat, ExPolicy>::call(
                 base_idx, it, count, HPX_FORWARD(F, f));
         }
 
@@ -1279,7 +1290,7 @@ namespace hpx::parallel::util {
             F&& f)
         {
             using cat = typename std::iterator_traits<Iter>::iterator_category;
-            return detail::loop_idx_n<cat>::call(
+            return detail::loop_idx_n<cat, ExPolicy>::call(
                 base_idx, it, count, tok, HPX_FORWARD(F, f));
         }
     };

From cbc7cf68067cba254274c00e3b5300f24ac0a8f2 Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <harihara.sn@gmail.com>
Date: Tue, 8 Aug 2023 16:20:45 -0500
Subject: [PATCH 4/6] removed ExPolicy as template for loop_pred (tag_invoke is
 being used for function call deduction)

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>
---
 .../hpx/parallel/unseq/simd_helpers.hpp       |  2 +-
 .../include/hpx/parallel/util/loop.hpp        | 27 +------------------
 2 files changed, 2 insertions(+), 27 deletions(-)

diff --git a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
index 4e2dd5131810..62f3caa7658a 100644
--- a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
@@ -13,6 +13,7 @@
 #include <hpx/parallel/unseq/reduce_helpers.hpp>
 #include <hpx/type_support/construct_at.hpp>
 
+
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
@@ -20,7 +21,6 @@
 #include <type_traits>
 #include <utility>
 
-// Please use static assert and enforce Iter to be Random Access Iterator
 namespace hpx::parallel::util {
     /*
         Compiler and Hardware should also support vector operations for IterDiff,
diff --git a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
index 4018c05ea12c..e4af118ab774 100644
--- a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
@@ -150,34 +150,9 @@ namespace hpx::parallel::util {
 
     ///////////////////////////////////////////////////////////////////////////
     namespace detail {
-        template <typename Iterator, typename ExPolicy>
-        struct loop_pred;
         // Helper class to repeatedly call a function starting from a given
         // iterator position till the predicate returns true.
         template <typename Iterator>
-        struct loop_pred<Iterator, void>
-        {
-            ///////////////////////////////////////////////////////////////////
-            template <typename Begin, typename End, typename Pred>
-            HPX_HOST_DEVICE HPX_FORCEINLINE static constexpr Begin call(
-                Begin it, End end, Pred&& pred)
-            {
-                for (/**/; it != end; ++it)
-                {
-                    if (HPX_INVOKE(pred, it))
-                        return it;
-                }
-                return it;
-            }
-        };
-    }    // namespace detail
-
-    ///////////////////////////////////////////////////////////////////////////
-    namespace detail {
-
-        // Helper class to repeatedly call a function starting from a given
-        // iterator position till the predicate returns true.
-        template <typename Iterator, typename ExPolicy>
         struct loop_pred
         {
             ///////////////////////////////////////////////////////////////////
@@ -205,7 +180,7 @@ namespace hpx::parallel::util {
         tag_fallback_invoke(hpx::parallel::util::loop_pred_t<ExPolicy>,
             Begin begin, End end, Pred&& pred)
         {
-            return detail::loop_pred<Begin, ExPolicy>::call(
+            return detail::loop_pred<Begin>::call(
                 begin, end, HPX_FORWARD(Pred, pred));
         }
     };

From 7f69717774fa2bb256fee6445e1f79a0a87e15f7 Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <harihara.sn@gmail.com>
Date: Tue, 8 Aug 2023 16:29:20 -0500
Subject: [PATCH 5/6] false changed to 0

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>
---
 .../algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
index 932867e03a9d..e2927525257c 100644
--- a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
+++ b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
@@ -23,7 +23,7 @@ void test_unseq_first_n1_dispatch2(std::size_t length, std::size_t first_index)
 {
     first_index = first_index % length;
 
-    std::vector<T> v(length, static_cast<T>(false));
+    std::vector<T> v(length, static_cast<T>(0));
     std::size_t i = 0;
 
     std::for_each(v.begin(), v.end(), [&](T& t) {

From d8096f0a3173a594c21cf6df1a993f39c5302ad1 Mon Sep 17 00:00:00 2001
From: Hari Hara Naveen S <harihara.sn@gmail.com>
Date: Tue, 8 Aug 2023 16:33:44 -0500
Subject: [PATCH 6/6] fixed cf

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>

fixed expolicy not accepting par_unseq

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>

cleanup changes

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>

fixing missing concept header

Signed-off-by: Hari Hara Naveen S <harihara.sn@gmail.com>
---
 .../hpx/parallel/algorithms/detail/find.hpp   |  3 --
 .../hpx/parallel/unseq/simd_helpers.hpp       |  1 -
 .../include/hpx/parallel/util/loop.hpp        | 32 +++++++------------
 .../algorithms/util/test_simd_helpers.cpp     |  2 +-
 4 files changed, 12 insertions(+), 26 deletions(-)

diff --git a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
index 8d80fe055f3c..30db28d9ac45 100644
--- a/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/algorithms/detail/find.hpp
@@ -45,7 +45,6 @@ namespace hpx::parallel::detail {
             std::size_t base_idx, FwdIter part_begin, std::size_t part_count,
             Token& tok, T const& val, Proj&& proj)
         {
-            // TODO
             util::loop_idx_n<ExPolicy>(base_idx, part_begin, part_count, tok,
                 [&val, &proj, &tok](auto& v, std::size_t i) -> void {
                     if (HPX_INVOKE(proj, v) == val)
@@ -102,7 +101,6 @@ namespace hpx::parallel::detail {
             sequential_find_if_t<ExPolicy>, FwdIter part_begin,
             std::size_t part_count, Token& tok, F&& op, Proj&& proj)
         {
-            // TODO
             util::loop_n<std::decay_t<ExPolicy>>(part_begin, part_count, tok,
                 [&op, &tok, &proj](auto const& curr) {
                     if (HPX_INVOKE(op, HPX_INVOKE(proj, *curr)))
@@ -118,7 +116,6 @@ namespace hpx::parallel::detail {
             FwdIter part_begin, std::size_t part_count, Token& tok, F&& f,
             Proj&& proj)
         {
-            // TODO
             util::loop_idx_n<ExPolicy>(base_idx, part_begin, part_count, tok,
                 [&f, &proj, &tok](auto& v, std::size_t i) -> void {
                     if (HPX_INVOKE(f, HPX_INVOKE(proj, v)))
diff --git a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
index 62f3caa7658a..cf7bf8380e86 100644
--- a/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/unseq/simd_helpers.hpp
@@ -13,7 +13,6 @@
 #include <hpx/parallel/unseq/reduce_helpers.hpp>
 #include <hpx/type_support/construct_at.hpp>
 
-
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
diff --git a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
index e4af118ab774..a3bf3659cfb1 100644
--- a/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
+++ b/libs/core/algorithms/include/hpx/parallel/util/loop.hpp
@@ -8,9 +8,9 @@
 
 #include <hpx/config.hpp>
 #include <hpx/assert.hpp>
+#include <hpx/concepts/concepts.hpp>
 #include <hpx/datastructures/tuple.hpp>
 #include <hpx/execution/traits/is_execution_policy.hpp>
-#include <hpx/executors/execution_policy.hpp>
 #include <hpx/functional/detail/invoke.hpp>
 #include <hpx/functional/detail/tag_fallback_invoke.hpp>
 #include <hpx/functional/invoke_result.hpp>
@@ -185,22 +185,12 @@ namespace hpx::parallel::util {
         }
     };
 
-    template <typename Begin, typename End, typename Pred,
-        HPX_CONCEPT_REQUIRES_(hpx::traits::is_random_access_iterator_v<Begin>)>
+    template <typename Begin, typename End, typename Pred, typename ExPolicy,
+        HPX_CONCEPT_REQUIRES_(hpx::traits::is_random_access_iterator_v<Begin>&&
+                hpx::is_unsequenced_execution_policy_v<ExPolicy>)>
     HPX_HOST_DEVICE HPX_FORCEINLINE Begin tag_invoke(
-        hpx::parallel::util::loop_pred_t<hpx::execution::unsequenced_policy>,
-        Begin HPX_RESTRICT begin, End HPX_RESTRICT end, Pred&& pred)
-    {
-        return unseq_first_n(
-            begin, std::distance(begin, end), HPX_FORWARD(Pred, pred));
-    }
-
-    template <typename Begin, typename End, typename Pred,
-        HPX_CONCEPT_REQUIRES_(hpx::traits::is_random_access_iterator_v<Begin>)>
-    HPX_HOST_DEVICE HPX_FORCEINLINE Begin tag_invoke(
-        hpx::parallel::util::loop_pred_t<
-            hpx::execution::unsequenced_task_policy>,
-        Begin HPX_RESTRICT begin, End HPX_RESTRICT end, Pred&& pred)
+        hpx::parallel::util::loop_pred_t<ExPolicy>, Begin HPX_RESTRICT begin,
+        End HPX_RESTRICT end, Pred&& pred)
     {
         return unseq_first_n(
             begin, std::distance(begin, end), HPX_FORWARD(Pred, pred));
@@ -1147,7 +1137,7 @@ namespace hpx::parallel::util {
 
         // Helper class to repeatedly call a function a given number of times
         // starting from a given iterator position.
-        template <typename IterCat, typename Dummy = void>
+        template <typename IterCat>
         struct loop_idx_n
         {
             ///////////////////////////////////////////////////////////////////
@@ -1185,8 +1175,8 @@ namespace hpx::parallel::util {
             }
         };
 
-        template <typename ExPolicy>
-        struct loop_idx_n<std::random_access_iterator_tag, ExPolicy>
+        template <>
+        struct loop_idx_n<std::random_access_iterator_tag>
         {
             ///////////////////////////////////////////////////////////////////
             // handle sequences of non-futures
@@ -1254,7 +1244,7 @@ namespace hpx::parallel::util {
             std::size_t base_idx, Iter it, std::size_t count, F&& f)
         {
             using cat = typename std::iterator_traits<Iter>::iterator_category;
-            return detail::loop_idx_n<cat, ExPolicy>::call(
+            return detail::loop_idx_n<cat>::call(
                 base_idx, it, count, HPX_FORWARD(F, f));
         }
 
@@ -1265,7 +1255,7 @@ namespace hpx::parallel::util {
             F&& f)
         {
             using cat = typename std::iterator_traits<Iter>::iterator_category;
-            return detail::loop_idx_n<cat, ExPolicy>::call(
+            return detail::loop_idx_n<cat>::call(
                 base_idx, it, count, tok, HPX_FORWARD(F, f));
         }
     };
diff --git a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
index e2927525257c..ab512b4c8316 100644
--- a/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
+++ b/libs/core/algorithms/tests/unit/algorithms/util/test_simd_helpers.cpp
@@ -23,7 +23,7 @@ void test_unseq_first_n1_dispatch2(std::size_t length, std::size_t first_index)
 {
     first_index = first_index % length;
 
-    std::vector<T> v(length, static_cast<T>(0));
+    std::vector<T> v(length);
     std::size_t i = 0;
 
     std::for_each(v.begin(), v.end(), [&](T& t) {