[libcxx-commits] [libcxx] [libc++] Optimize ranges::{for_each, for_each_n} for segmented iterators (PR #132896)

[Peng Liu via libcxx-commits]

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@@ -33,15 +35,19 @@ int main(int argc, char** argv) {
 
             for ([[maybe_unused]] auto _ : st) {
               benchmark::DoNotOptimize(c);
-              auto result = for_each(first, last, [](int& x) { x = std::clamp(x, 10, 100); });
+              auto result = for_each(first, last, [](ElemType& x) { x = std::clamp<ElemType>(x, 10, 100); });
               benchmark::DoNotOptimize(result);
             }
           })
           ->Arg(8)
           ->Arg(32)
           ->Arg(50) // non power-of-two
+          ->Arg(1024)
+          ->Arg(4096)
           ->Arg(8192)
-          ->Arg(1 << 20);
+          ->Arg(1 << 14)
+          ->Arg(1 << 16)
+          ->Arg(1 << 18);
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winner245 wrote:

Previously, we were running a test case with a very large `n = (1 << 20)`. To save some time, I replaced this large test case with 3 smaller test cases with `n = (1 << 14)`, `1 << 16`, `1 << 18`. I think the total execution time of these three test cases is actually lower than running a single test case with `n = (1 << 20)`. Please let me know if I misunderstood you. 

https://github.com/llvm/llvm-project/pull/132896