remove.cpp

// Copyright 2020 The Division Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Author dietoad@gmail.com && firedtoad@gmail.com

#include <benchmark/benchmark.h>
#include <list>
#include <string>
#include <vector>

#include <llvm/ADT/SmallVector.h>

constexpr int N = 1000;

template <class V> void init(V &v1)
{
    v1.resize(N);
    for (auto i = 0; i < N; i++)
    {
        v1[i] = std::to_string(i);
    }
}

static unsigned long xorshf96()
{ /* A George Marsaglia generator, period 2^96-1 */
    static unsigned long x = 123456789, y = 362436069, z = 521288629;
    unsigned long t;

    x ^= x << 16;
    x ^= x >> 5;
    x ^= x << 1;

    t = x;
    x = y;
    y = z;

    z = t ^ x ^ y;
    return z;
}

static inline unsigned long random_()
{
    return xorshf96();
}

void init(std::list<std::string> &v1)
{
    for (auto i = 0; i < N; i++)
    {
        v1.push_back(std::to_string(i * 1000));
    }
}

static void BM_erase(benchmark::State &state)
{
    std::vector<std::string> vec;
    init(vec);
    for (auto _ : state)
    {
        auto idx   = random_() % vec.size();
        auto start = std::next(vec.begin(), idx);
        auto val   = *start;
        vec.erase(start);
        vec.push_back(val);
    }
}

static void BM_eraseSmall(benchmark::State &state)
{
    llvm::SmallVector<std::string, N> vec;
    init(vec);
    for (auto _ : state)
    {
        auto idx   = random_() % vec.size();
        auto start = std::next(vec.begin(), idx);
        auto val   = *start;
        vec.erase(start);
        vec.push_back(val);
    }
}

static void BM_swap_pop(benchmark::State &state)
{
    std::vector<std::string> vec;
    init(vec);
    for (auto _ : state)
    {
        auto idx   = random_() % vec.size();
        auto start = std::next(vec.begin(), idx);
        auto val   = *start;
        std::swap(*start, vec.back());
        vec.pop_back();
        vec.push_back(val);
    }
}

static void BM_swap_popSmall(benchmark::State &state)
{
    llvm::SmallVector<std::string, N> vec;
    init(vec);
    for (auto _ : state)
    {
        auto idx   = random_() % vec.size();
        auto start = std::next(vec.begin(), idx);
        auto val   = *start;
        std::swap(*start, vec.back());
        vec.pop_back();
        vec.push_back(val);
    }
}

static void BM_list(benchmark::State &state)
{
    std::list<std::string> vec;
    init(vec);
    for (auto _ : state)
    {
        auto idx   = random_() % vec.size();
        auto start = std::next(vec.begin(), idx);
        auto val   = *start;
        vec.erase(start);
        vec.push_back(val);
    }
}

BENCHMARK(BM_erase);
BENCHMARK(BM_eraseSmall);
BENCHMARK(BM_swap_pop);
BENCHMARK(BM_swap_popSmall);
BENCHMARK(BM_list);

int main(int argc, char **argv)
{
    benchmark::Initialize(&argc, argv);
    benchmark::RunSpecifiedBenchmarks();
    return 0;
}