From 9af0e6c6536d26049354c877f144dc1a93cf148b Mon Sep 17 00:00:00 2001
From: Håvard Pettersen <havardpe@yahooinc.com>
Date: Tue, 15 Nov 2022 14:40:38 +0000
Subject: adjust generator bench

also benchmark Sequence alternative
---
 .../src/tests/coro/generator/generator_bench.cpp   | 99 +++++++++++++++-------
 1 file changed, 70 insertions(+), 29 deletions(-)

(limited to 'vespalib/src/tests')

diff --git a/vespalib/src/tests/coro/generator/generator_bench.cpp b/vespalib/src/tests/coro/generator/generator_bench.cpp
index 664132b7ba4..7671a48b2e6 100644
--- a/vespalib/src/tests/coro/generator/generator_bench.cpp
+++ b/vespalib/src/tests/coro/generator/generator_bench.cpp
@@ -2,21 +2,14 @@
 
 #include <vespa/vespalib/coro/generator.h>
 #include <vespa/vespalib/util/benchmark_timer.h>
+#include <vespa/vespalib/util/sequence.h>
 #include <vespa/vespalib/gtest/gtest.h>
 #include <ranges>
 #include <vector>
 
 using vespalib::coro::Generator;
 using vespalib::BenchmarkTimer;
-
-std::vector<size_t> make_data() __attribute__((noinline));
-std::vector<size_t> make_data(size_t size) {
-    std::vector<size_t> data;
-    for (size_t i = 0; i < size; ++i) {
-        data.push_back(i);
-    }
-    return data;
-}
+using vespalib::Sequence;
 
 template <std::ranges::input_range T>
 size_t calc_sum(T&& values) {
@@ -27,32 +20,80 @@ size_t calc_sum(T&& values) {
     return sum;
 }
 
-size_t calc_sum_direct(const std::vector<size_t> &values) {
-    return calc_sum(values);
+size_t calc_sum(Sequence<size_t> &seq) {
+    size_t sum = 0;
+    for (; seq.valid(); seq.next()) {
+        sum += seq.get();
+    }
+    return sum;
 }
 
-size_t calc_sum_wrapped(const std::vector<size_t> &values) {
-    return calc_sum([](const std::vector<size_t> &inner_values)->Generator<size_t>
-                    {
-                        for (auto&& value: inner_values) {
-                            co_yield value;
-                        }
-                    }(values));
+struct ValueRange {
+    using iterator_concept = std::input_iterator_tag;
+    using difference_type = std::ptrdiff_t;
+    using value_type = size_t;
+    size_t first;
+    size_t last;
+    ValueRange() noexcept : first(0), last(0) {}
+    ValueRange(size_t first_in, size_t last_in) noexcept
+      : first(first_in), last(last_in) {}
+    auto begin() noexcept { return ValueRange(first, last); }
+    auto end() const noexcept { return std::default_sentinel_t(); }
+    bool operator==(std::default_sentinel_t) const noexcept { return (first == last); }
+    ValueRange &operator++() noexcept { ++first; return *this; }
+    void operator++(int) noexcept { operator++(); }
+    size_t operator*() const noexcept { return first; }
+};
+
+size_t calc_sum_direct(size_t first, size_t last) {
+    return calc_sum(ValueRange(first, last));
+}
+
+Generator<size_t> gen_values(size_t first, size_t last) {
+    for (size_t i = first; i < last; ++i) {
+        co_yield i;
+    }
+}
+
+size_t calc_sum_generator(size_t first, size_t last) {
+    return calc_sum(gen_values(first, last));
+}
+
+struct MySeq : Sequence<size_t> {
+    size_t first;
+    size_t last;
+    MySeq(size_t first_in, size_t last_in)
+      : first(first_in), last(last_in) {}
+    bool valid() const override { return (first < last); }
+    size_t get() const override { return first; }
+    void next() override { ++first; }
+};
+
+size_t calc_sum_sequence(size_t first, size_t last) {
+    MySeq seq(first, last);
+    return calc_sum(seq);
 }
 
-TEST(GeneratorBench, direct_vs_wrapped_vector_for_loop) {
-    std::vector<size_t> data = make_data(100000);
-    double direct_ms = BenchmarkTimer::benchmark([&data](){
-                                                     size_t sink = calc_sum_direct(data);
-                                                     (void) sink;
+TEST(GeneratorBench, direct_vs_generated_for_loop) {
+    size_t first = 0;
+    size_t last = 100000;
+    size_t res_direct = 0;
+    size_t res_generator = 1;
+    size_t res_sequence = 2;
+    double direct_ms = BenchmarkTimer::benchmark([first,last,&res_direct](){
+                                                     res_direct = calc_sum_direct(first, last);
                                                  }, 5.0) * 1000.0;
     fprintf(stderr, "direct: %g ms\n", direct_ms);
-    double wrapped_ms = BenchmarkTimer::benchmark([&data](){
-                                                      size_t sink = calc_sum_wrapped(data);
-                                                      (void) sink;
-                                                  }, 5.0) * 1000.0;
-    fprintf(stderr, "wrapped: %g ms\n", wrapped_ms);
-    fprintf(stderr, "ratio: %g\n", (wrapped_ms/direct_ms));
+    double generator_ms = BenchmarkTimer::benchmark([first,last,&res_generator](){
+                                                        res_generator = calc_sum_generator(first, last);
+                                                    }, 5.0) * 1000.0;
+    fprintf(stderr, "generator: %g ms\n", generator_ms);
+    double sequence_ms = BenchmarkTimer::benchmark([first,last,&res_sequence](){
+                                                       res_sequence = calc_sum_sequence(first, last);
+                                                   }, 5.0) * 1000.0;
+    fprintf(stderr, "sequence: %g ms\n", sequence_ms);
+    fprintf(stderr, "ratio (generator/direct): %g\n", (generator_ms/direct_ms));
+    fprintf(stderr, "ratio (generator/sequence): %g\n", (generator_ms/sequence_ms));
 }
 
 GTEST_MAIN_RUN_ALL_TESTS()
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