[libcxx-commits] [libcxx] cdc8e8d - [libc++] Add more benchmarks for the associative container hint interfaces (#162840)

[via libcxx-commits]

Author: Nikolas Klauser
Date: 2025-10-13T10:50:58+02:00
New Revision: cdc8e8d092619b318d69c61a941246a31c8cd26f

URL: https://github.com/llvm/llvm-project/commit/cdc8e8d092619b318d69c61a941246a31c8cd26f
DIFF: https://github.com/llvm/llvm-project/commit/cdc8e8d092619b318d69c61a941246a31c8cd26f.diff

LOG: [libc++] Add more benchmarks for the associative container hint interfaces (#162840)

The current benchmarks test a very specific case, which makes them
rather misleading. This adds new benchmarks so we have better coverage.

Added: 
    

Modified: 
    libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h

Removed: 
    


################################################################################
diff  --git a/libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h b/libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h
index b39569812640b..22a6d0d753b0c 100644
--- a/libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h
+++ b/libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h
@@ -305,11 +305,19 @@ void associative_container_benchmarks(std::string container) {
   // The insert(hint, ...) methods are only relevant for ordered containers, and we lack
   // a good way to compute a hint for unordered ones.
   if constexpr (is_ordered_container) {
-    bench("insert(hint, value) (good hint)", [=](auto& st) {
+    auto insert_good_hint_bench = [=](bool bench_end_iter, auto& st) {
       const std::size_t size = st.range(0);
       std::vector<Value> in  = make_value_types(generate_unique_keys(size + 1));
-      Value to_insert        = in.back();
-      in.pop_back();
+      auto skipped_val       = bench_end_iter ? in.size() - 1 : in.size() / 2;
+      Value to_insert        = in[skipped_val];
+      { // Remove the element
+        std::vector<Value> tmp;
+        tmp.reserve(in.size() - 1);
+        for (size_t i = 0; i != in.size(); ++i)
+          if (i != skipped_val)
+            tmp.emplace_back(in[i]);
+        in = std::move(tmp);
+      }
 
       std::vector<Container> c(BatchSize, Container(in.begin(), in.end()));
       typename Container::iterator hints[BatchSize];
@@ -332,13 +340,23 @@ void associative_container_benchmarks(std::string container) {
         }
         st.ResumeTiming();
       }
-    });
+    };
+    bench("insert(hint, value) (good hint, end)", [=](auto& state) { insert_good_hint_bench(true, state); });
+    bench("insert(hint, value) (good hint, middle)", [=](auto& state) { insert_good_hint_bench(false, state); });
 
-    bench("insert(hint, value) (bad hint)", [=](auto& st) {
+    auto insert_bad_hint_bench = [=](bool bench_end_iter, auto& st) {
       const std::size_t size = st.range(0);
       std::vector<Value> in  = make_value_types(generate_unique_keys(size + 1));
-      Value to_insert        = in.back();
-      in.pop_back();
+      auto skipped_val       = bench_end_iter ? in.size() - 1 : in.size() / 2;
+      Value to_insert        = in[skipped_val];
+      { // Remove the element
+        std::vector<Value> tmp;
+        tmp.reserve(in.size() - 1);
+        for (size_t i = 0; i != in.size(); ++i)
+          if (i != skipped_val)
+            tmp.emplace_back(in[i]);
+        in = std::move(tmp);
+      }
       std::vector<Container> c(BatchSize, Container(in.begin(), in.end()));
 
       while (st.KeepRunningBatch(BatchSize)) {
@@ -355,7 +373,10 @@ void associative_container_benchmarks(std::string container) {
         }
         st.ResumeTiming();
       }
-    });
+    };
+
+    bench("insert(hint, value) (bad hint, end)", [=](auto& state) { insert_bad_hint_bench(true, state); });
+    bench("insert(hint, value) (bad hint, middle)", [=](auto& state) { insert_bad_hint_bench(false, state); });
   }
 
   bench("insert(iterator, iterator) (all new keys)", [=](auto& st) {