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refine 'likely' test.
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wangjiacai 2023-02-12 00:15:06 +08:00
parent e5110406ec
commit 5f339eaa55
1 changed files with 45 additions and 37 deletions
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82
misc/likely.cpp
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@ -1,85 +1,93 @@
#include <iostream>
#include <thread>
#include <chrono>
#include <sys/time.h>
#include <limits.h>
#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
using namespace std;
#define SIZE 500000000
const int SIZE = 128 * 1024 * 1024;
const int RANGE = RAND_MAX / 2;
int arr[SIZE];
void func(int *pval)
void func1(int *pval)
{
double ret = 0;
int big = 0, small = 0;
timeval start, end;
gettimeofday(&start, nullptr);
while (*pval)
for (int idx = 0; idx < SIZE; idx++)
{
if (((*pval) == 256))
ret = ret + 1234;
if (((pval[idx]) > RANGE / 2))
big++;
else
ret = ret + 5678;
pval++;
small++;
}
gettimeofday(&end, nullptr);
double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
cout << __func__ << " duration: " << usec << ", big: " << big << ", small:" << small << endl;
}
void func2(int *pval)
{
int big = 0, small = 0;
timeval start, end;
gettimeofday(&start, nullptr);
for (int idx = 0; idx < SIZE; idx++)
{
if (((pval[idx]) <= RANGE / 2))
small++;
else
big++;
}
gettimeofday(&end, nullptr);
double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
cout << __func__ << " duration: " << usec << ", big: " << big << ", small:" << small << endl;
}
void func_likely(int *pval)
{
double ret = 0;
int big = 0, small = 0;
timeval start, end;
gettimeofday(&start, nullptr);
while (*pval)
for (int idx = 0; idx < SIZE; idx++)
{
if (likely((*pval) == 256))
ret = ret + 1234;
if (likely((pval[idx]) > RANGE / 2))
big++;
else
ret = ret + 5678;
pval++;
small++;
}
gettimeofday(&end, nullptr);
double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
cout << __func__ << " duration: " << usec << ", big: " << big << ", small:" << small << endl;
}
void func_unlikely(int *pval)
{
double ret = 0;
int big = 0, small = 0;
timeval start, end;
gettimeofday(&start, nullptr);
while (*pval)
for (int idx = 0; idx < SIZE; idx++)
{
if (unlikely((*pval) == 256))
ret = ret + 1234;
if (unlikely((pval[idx]) > RANGE / 2))
big++;
else
ret = ret + 5678;
pval++;
small++;
}
gettimeofday(&end, nullptr);
double usec = (end.tv_sec - start.tv_sec) + (double)(end.tv_usec - start.tv_usec) / 1000000;
cout << __func__ << " duration: " << usec << ", ret: " << ret << endl;
cout << __func__ << " duration: " << usec << ", big: " << big << ", small:" << small << endl;
}
int main()
{
srand(time(nullptr));
for (int i = 0; i < SIZE; i++)
{
if (i % 1000 == 0)
*(arr + i) = 256;
else
*(arr + i) = 128;
arr[i] = (rand() % (RANGE + 1)) + 0.499 * RANGE;
}
arr[SIZE - 1] = 0;
std::thread t1(func, arr);
std::thread t2(func_likely, arr);
std::thread t3(func_unlikely, arr);
t1.join();
t2.join();
t3.join();
func1(arr);
func2(arr);
func_likely(arr);
func_unlikely(arr);
}