From 0f5d94a81aacf0c11c5c3c286842e23f3e002640 Mon Sep 17 00:00:00 2001
From: Viral <viralrbhadeshiya@gmail.com>
Date: Mon, 8 Dec 2025 09:19:46 -0800
Subject: [PATCH 1/2] smoke test for exclusive_scan

---
 test/stdpar/tests/exclusive_scan.cpp | 46 ++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 test/stdpar/tests/exclusive_scan.cpp

diff --git a/test/stdpar/tests/exclusive_scan.cpp b/test/stdpar/tests/exclusive_scan.cpp
new file mode 100644
index 00000000000..b92eb3e70f6
--- /dev/null
+++ b/test/stdpar/tests/exclusive_scan.cpp
@@ -0,0 +1,46 @@
+#include <cstddef>
+#include <execution>
+#include <numeric>
+#include <vector>
+
+int main()
+{
+  constexpr std::size_t N = 1 << 16;
+
+  std::vector<int> in(N);
+  std::vector<int> out(N);
+
+  for (std::size_t i = 0; i < N; ++i)
+  {
+    in[i] = static_cast<int>(i + 1);
+  }
+
+  // exclusive_scan with default initial value (0)
+  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), 0);
+
+  int running_sum = 0;
+  for (std::size_t i = 0; i < N; ++i)
+  {
+    if (out[i] != running_sum)
+    {
+      return 1;
+    }
+    running_sum += in[i];
+  }
+
+  // exclusive_scan with non-zero initial value
+  const int init = 42;
+  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), init);
+
+  running_sum = init;
+  for (std::size_t i = 0; i < N; ++i)
+  {
+    if (out[i] != running_sum)
+    {
+      return 1;
+    }
+    running_sum += in[i];
+  }
+
+  return 0;
+}

From b51f01ee38d4612584833bc056b7ab706dbdbc10 Mon Sep 17 00:00:00 2001
From: Viral <viralrbhadeshiya@gmail.com>
Date: Thu, 11 Dec 2025 12:18:44 -0800
Subject: [PATCH 2/2] added test cases for binary ops

---
 test/stdpar/tests/exclusive_scan.cpp | 46 ++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/test/stdpar/tests/exclusive_scan.cpp b/test/stdpar/tests/exclusive_scan.cpp
index b92eb3e70f6..a4273cade20 100644
--- a/test/stdpar/tests/exclusive_scan.cpp
+++ b/test/stdpar/tests/exclusive_scan.cpp
@@ -1,5 +1,6 @@
 #include <cstddef>
 #include <execution>
+#include <functional>
 #include <numeric>
 #include <vector>
 
@@ -10,15 +11,13 @@ int main()
   std::vector<int> in(N);
   std::vector<int> out(N);
 
-  for (std::size_t i = 0; i < N; ++i)
-  {
-    in[i] = static_cast<int>(i + 1);
-  }
+  std::iota(in.begin(), in.end(), 1);
 
-  // exclusive_scan with default initial value (0)
-  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), 0);
+  // exclusive_scan with non-zero initial value
+  const int init = 42;
+  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), init);
 
-  int running_sum = 0;
+  int running_sum = init;
   for (std::size_t i = 0; i < N; ++i)
   {
     if (out[i] != running_sum)
@@ -28,18 +27,39 @@ int main()
     running_sum += in[i];
   }
 
-  // exclusive_scan with non-zero initial value
-  const int init = 42;
-  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), init);
+  // exclusive_scan with initial value & binary ops
+  const int mul_init = 1;
+  std::exclusive_scan(std::execution::par, in.begin(), in.end(), out.begin(), mul_init, std::multiplies<int>{});
 
-  running_sum = init;
+  int expected = mul_init;
   for (std::size_t i = 0; i < N; ++i)
   {
-    if (out[i] != running_sum)
+    if (out[i] != expected)
+    {
+      return 1;
+    }
+    expected *= 2;
+  }
+
+  // exclusive_scan with initial value & custom binary ops
+  const int init2 = 7;
+  std::exclusive_scan(
+    std::execution::par,
+    in.begin(),
+    in.end(),
+    out.begin(),
+    init2,
+    [](int lhs, int rhs) {
+      return lhs + rhs + 1;
+    })
+
+    for (std::size_t i = 0; i < N; ++i)
+  {
+    const int expected = init2 + static_cast<int>(2 * i);
+    if (out[i] != expected)
     {
       return 1;
     }
-    running_sum += in[i];
   }
 
   return 0;