85 lines
2.0 KiB
C++
85 lines
2.0 KiB
C++
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#include <iostream>
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#include <thread>
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#include <chrono>
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#include <sys/time.h>
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#include <limits.h>
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#define likely(x) __builtin_expect(!!(x), 1)
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#define unlikely(x) __builtin_expect(!!(x), 0)
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using namespace std;
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#define SIZE 500000000
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int arr[SIZE];
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void func(int *pval)
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{
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double ret = 0;
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timeval start, end;
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gettimeofday(&start, nullptr);
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while (*pval)
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{
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if (((*pval) == 256))
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ret = ret + 1234;
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else
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ret = ret + 5678;
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pval++;
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}
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gettimeofday(&end, nullptr);
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double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
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cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
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}
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void func_likely(int *pval)
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{
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double ret = 0;
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timeval start, end;
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gettimeofday(&start, nullptr);
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while (*pval)
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{
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if (likely((*pval) == 256))
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ret = ret + 1234;
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else
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ret = ret + 5678;
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pval++;
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}
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gettimeofday(&end, nullptr);
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double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
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cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
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}
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void func_unlikely(int *pval)
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{
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double ret = 0;
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timeval start, end;
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gettimeofday(&start, nullptr);
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while (*pval)
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{
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if (unlikely((*pval) == 256))
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ret = ret + 1234;
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else
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ret = ret + 5678;
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pval++;
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}
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gettimeofday(&end, nullptr);
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double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
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cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
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}
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int main()
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{
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for (int i = 0; i < SIZE; i++)
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{
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if (i % 1000 == 0)
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*(arr + i) = 256;
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else
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*(arr + i) = 128;
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}
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arr[SIZE - 1] = 0;
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std::thread t1(func, arr);
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std::thread t2(func_likely, arr);
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std::thread t3(func_unlikely, arr);
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t1.join();
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t2.join();
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t3.join();
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}
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