Fix schedule_all chunking for small ranges

include/exec/static_thread_pool.hpp

@@ -1749,7 +1749,8 @@ namespace experimental::execution
           std::size_t nthreads     = this->pool_.available_parallelism();
           bwos_params params       = this->pool_.params();
           std::size_t local_size   = params.blockSize * params.numBlocks;
-          std::size_t chunk_size   = __umin({size / nthreads, local_size * nthreads});
+          std::size_t chunk_size =
+            __umax({std::size_t{1}, __umin({size / nthreads, local_size * nthreads})});
           auto&       remote_queue = *this->pool_.get_remote_queue();
           auto        it           = std::ranges::begin(this->range_);
           std::size_t i0           = 0;
@@ -1765,6 +1766,7 @@ namespace experimental::execution
 
             std::unique_lock lock{this->start_mutex_};
             this->pool_.bulk_enqueue(remote_queue, std::move(this->tasks_), this->tasks_size_);
+            this->tasks_size_ = 0;
             lock.unlock();
             i0 += chunk_size;
           }
@@ -1778,6 +1780,7 @@ namespace experimental::execution
           std::unique_lock lock{this->start_mutex_};
           this->has_started_ = true;
           this->pool_.bulk_enqueue(remote_queue, std::move(this->tasks_), this->tasks_size_);
+          this->tasks_size_ = 0;
         }
       };
 

test/exec/test_static_thread_pool.cpp

@@ -1,8 +1,12 @@
 #include "catch2/catch_all.hpp"
+#include <exec/sequence/ignore_all_values.hpp>
+#include <exec/sequence/transform_each.hpp>
 #include <exec/static_thread_pool.hpp>
 #include <stdexec/execution.hpp>
 
+#include <array>
 #include <mutex>
+#include <ranges>
 #include <thread>
 #include <unordered_set>
 namespace ex = STDEXEC;
@@ -65,3 +69,22 @@ TEST_CASE("bulk on static_thread_pool executes on multiple threads, take 2",
   ex::sync_wait(std::move(sender));
   REQUIRE(thread_ids.size() == num_of_threads);
 }
+
+TEST_CASE("schedule_all on static_thread_pool handles fewer items than threads",
+          "[types][static_thread_pool]")
+{
+  constexpr size_t const   num_of_threads = 4;
+  exec::static_thread_pool pool{num_of_threads};
+  std::array<bool, 3>      visited{};
+
+  auto sender = exec::schedule_all(pool, std::views::iota(size_t{0}, visited.size()))
+              | exec::transform_each(ex::then([&](size_t i) noexcept { visited[i] = true; }))
+              | exec::ignore_all_values();
+
+  ex::sync_wait(std::move(sender));
+
+  for (bool item_visited: visited)
+  {
+    REQUIRE(item_visited);
+  }
+}