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ldionneldionne
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Reduce the variance in lookup benchmarks
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-47
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+42
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‎libcxx/test/benchmarks/containers/associative/associative_container_benchmarks.h‎

Lines changed: 42 additions & 47 deletions
Original file line numberDiff line numberDiff line change
@@ -348,14 +348,17 @@ void associative_container_benchmarks(std::string container) {
348348

349349
bench("erase(key) (non-existent)", [=](auto& st) {
350350
const std::size_t size = st.range(0);
351-
std::vector<Value> in = make_value_types(generate_unique_keys(size + 1));
352-
Value element = in.back();
353-
in.pop_back();
351+
std::vector<Value> in = make_value_types(generate_unique_keys(size + BatchSize));
352+
std::vector<Key> keys;
353+
for (std::size_t i = 0; i != BatchSize; ++i) {
354+
keys.push_back(get_key(in.back()));
355+
in.pop_back();
356+
}
354357
Container c(in.begin(), in.end());
355358

356359
while (st.KeepRunningBatch(BatchSize)) {
357360
for (std::size_t i = 0; i != BatchSize; ++i) {
358-
auto result = c.erase(get_key(element));
361+
auto result = c.erase(keys[i]);
359362
benchmark::DoNotOptimize(result);
360363
benchmark::DoNotOptimize(c);
361364
benchmark::ClobberMemory();
@@ -449,16 +452,20 @@ void associative_container_benchmarks(std::string container) {
449452
/////////////////////////
450453
// Query
451454
/////////////////////////
452-
auto bench_with_existent_key = [=](auto func) {
455+
auto with_existent_key = [=](auto func) {
453456
return [=](auto& st) {
454457
const std::size_t size = st.range(0);
455458
std::vector<Value> in = make_value_types(generate_unique_keys(size));
456-
Value element = in[in.size() / 2]; // pick any element
459+
// Pick any `BatchSize` number of elements
460+
std::vector<Key> keys;
461+
for (std::size_t i = 0; i < in.size(); i += (in.size() / BatchSize)) {
462+
keys.push_back(get_key(in.at(i)));
463+
}
457464
Container c(in.begin(), in.end());
458465

459466
while (st.KeepRunningBatch(BatchSize)) {
460467
for (std::size_t i = 0; i != BatchSize; ++i) {
461-
auto result = func(c, element);
468+
auto result = func(c, keys[i]);
462469
benchmark::DoNotOptimize(c);
463470
benchmark::DoNotOptimize(result);
464471
benchmark::ClobberMemory();
@@ -467,17 +474,20 @@ void associative_container_benchmarks(std::string container) {
467474
};
468475
};
469476

470-
auto bench_with_nonexistent_key = [=](auto func) {
477+
auto with_nonexistent_key = [=](auto func) {
471478
return [=](auto& st) {
472479
const std::size_t size = st.range(0);
473-
std::vector<Value> in = make_value_types(generate_unique_keys(size + 1));
474-
Value element = in.back();
475-
in.pop_back();
480+
std::vector<Value> in = make_value_types(generate_unique_keys(size + BatchSize));
481+
std::vector<Key> keys;
482+
for (std::size_t i = 0; i != BatchSize; ++i) {
483+
keys.push_back(get_key(in.back()));
484+
in.pop_back();
485+
}
476486
Container c(in.begin(), in.end());
477487

478488
while (st.KeepRunningBatch(BatchSize)) {
479489
for (std::size_t i = 0; i != BatchSize; ++i) {
480-
auto result = func(c, element);
490+
auto result = func(c, keys[i]);
481491
benchmark::DoNotOptimize(c);
482492
benchmark::DoNotOptimize(result);
483493
benchmark::ClobberMemory();
@@ -486,45 +496,30 @@ void associative_container_benchmarks(std::string container) {
486496
};
487497
};
488498

489-
bench("find(key) (existent)",
490-
bench_with_existent_key([=](Container const& c, Value const& element) { return c.find(get_key(element)); }));
491-
bench("find(key) (non-existent)",
492-
bench_with_nonexistent_key([=](Container const& c, Value const& element) { return c.find(get_key(element)); }));
499+
auto find = [](Container const& c, Key const& key) { return c.find(key); };
500+
bench("find(key) (existent)", with_existent_key(find));
501+
bench("find(key) (non-existent)", with_nonexistent_key(find));
493502

494-
bench("count(key) (existent)",
495-
bench_with_existent_key([=](Container const& c, Value const& element) { return c.count(get_key(element)); }));
496-
bench("count(key) (non-existent)", bench_with_nonexistent_key([=](Container const& c, Value const& element) {
497-
return c.count(get_key(element));
498-
}));
503+
auto count = [](Container const& c, Key const& key) { return c.count(key); };
504+
bench("count(key) (existent)", with_existent_key(count));
505+
bench("count(key) (non-existent)", with_nonexistent_key(count));
499506

500-
bench("contains(key) (existent)", bench_with_existent_key([=](Container const& c, Value const& element) {
501-
return c.contains(get_key(element));
502-
}));
503-
bench("contains(key) (non-existent)", bench_with_nonexistent_key([=](Container const& c, Value const& element) {
504-
return c.contains(get_key(element));
505-
}));
507+
auto contains = [](Container const& c, Key const& key) { return c.contains(key); };
508+
bench("contains(key) (existent)", with_existent_key(contains));
509+
bench("contains(key) (non-existent)", with_nonexistent_key(contains));
506510

507511
if constexpr (is_ordered_container) {
508-
bench("lower_bound(key) (existent)", bench_with_existent_key([=](Container const& c, Value const& element) {
509-
return c.lower_bound(get_key(element));
510-
}));
511-
bench("lower_bound(key) (non-existent)", bench_with_nonexistent_key([=](Container const& c, Value const& element) {
512-
return c.lower_bound(get_key(element));
513-
}));
514-
515-
bench("upper_bound(key) (existent)", bench_with_existent_key([=](Container const& c, Value const& element) {
516-
return c.upper_bound(get_key(element));
517-
}));
518-
bench("upper_bound(key) (non-existent)", bench_with_nonexistent_key([=](Container const& c, Value const& element) {
519-
return c.upper_bound(get_key(element));
520-
}));
521-
522-
bench("equal_range(key) (existent)", bench_with_existent_key([=](Container const& c, Value const& element) {
523-
return c.equal_range(get_key(element));
524-
}));
525-
bench("equal_range(key) (non-existent)", bench_with_nonexistent_key([=](Container const& c, Value const& element) {
526-
return c.equal_range(get_key(element));
527-
}));
512+
auto lower_bound = [](Container const& c, Key const& key) { return c.lower_bound(key); };
513+
bench("lower_bound(key) (existent)", with_existent_key(lower_bound));
514+
bench("lower_bound(key) (non-existent)", with_nonexistent_key(lower_bound));
515+
516+
auto upper_bound = [](Container const& c, Key const& key) { return c.upper_bound(key); };
517+
bench("upper_bound(key) (existent)", with_existent_key(upper_bound));
518+
bench("upper_bound(key) (non-existent)", with_nonexistent_key(upper_bound));
519+
520+
auto equal_range = [](Container const& c, Key const& key) { return c.equal_range(key); };
521+
bench("equal_range(key) (existent)", with_existent_key(equal_range));
522+
bench("equal_range(key) (non-existent)", with_nonexistent_key(equal_range));
528523
}
529524
}
530525

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