[英]threaded matrix multiplication function
I'm trying to write two matrix multiplication functions, one standard and one that is threaded. 我正在尝试编写两个矩阵乘法函数,一个是标准函数,另一个是线程化的。 However, I can't figure out how to call the threaded function correctly.
但是,我不知道如何正确调用线程函数。
Here is the code: 这是代码:
#include <iostream>
#include <future>
#include <sys/time.h>
#include <stdio.h>
#include <thread>
using namespace std;
double get_wallTime() {
struct timeval tp;
gettimeofday(&tp, NULL);
return (double) (tp.tv_sec + tp.tv_usec/1000000.0);
}
static void matrixMultiply(double** a, double** b, double** product, int size) {
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++) {
for (int k = 0; k < size; k++) {
product[i][j] += a[i][k] * b[k][j];
}
}
}
}
static void matrixMultiplyThreaded(double** a, double** b, double** product, int dimLower, int dimUpper, int dim) {
for (int i = dimLower; i < dimUpper; i++) {
for (int j = 0; j < dim; j++) {
for (int k = 0; k < dim; k++) {
product[i][j] += a[i][k] * b[k][j];
}
}
}
}
int main(int argc, char *argv[]) {
if (argc < 3) {
cout << "Not enough arguments.";
}
int numTimes = atoi(argv[1]);
char *threadOrNo = argv[2];
int size = atoi(argv[3]);
double a[size][size], b[size][size] = {};
double product[size][size] = {};
for (int i=0; i<size; i++) {
for (int j=0; j < size; j++) {
a[i][j] = 2;
b[i][j] = 3;
}
}
double t1 = get_wallTime();
if (*threadOrNo == 'y') {
int dim1 = size / 2;
for (int n = 0; n < numTimes; n++) {
std::thread first (matrixMultiplyThreaded, a, b, product, 0, dim1, size);
std::thread second (matrixMultiplyThreaded, a, b, product, dim1, size, size);
first.join();
second.join();
}
}
else {
for (int m = 0; m < numTimes; m++) {
matrixMultiply(a[size][size],b[size][size], product[size][size], size);
}
}
double t2 = get_wallTime();
double totalTime = t2 - t1;
cout << "time : " << totalTime;
}
If anyone could give any advice I would be eternally grateful. 如果有人可以提供任何建议,我将永远感激不已。 Specifically, what's the right way to implement threads for the threaded function?
具体来说,为线程函数实现线程的正确方法是什么?
Here is the first error message I receive, which I've tried to fix several times: 这是我收到的第一条错误消息,我已尝试修复多次:
multiplyMatrix.cpp: In function 'int main(int, char**)':
multiplyMatrix.cpp:64:82: error: no matching function for call to 'std::thread::thread(void (&)(double**, double**, double**, int, int, int), double [size][size], double [size][size], double [size][size], int, int&, int&)'
std::thread first (matrixMultiplyThreaded, a, b, product, 0, dim1, size);
I couldn't compile your code because of other errors, but for the part that launches threads, you should use lambdas: 由于其他错误,我无法编译您的代码,但是对于启动线程的部分,您应该使用lambda:
std::thread first([=]() { matrixMultiplyThreaded(a, b, product, 0, dim1, size); });
std::thread second([=]() { matrixMultiplyThreaded(a, b, product, dim1, size, size); });
Among other errors, you can't statically allocate arrays ( a
, b
and product
) with a variable (which is a dynamic value). 除其他错误外,您不能为变量(动态值)静态分配数组(
a
, b
和product
)。 Do as follows: 进行如下操作:
double **a = new double*[size];
double **b = new double*[size];
double **product = new double*[size];
for (int i = 0; i < size; i++)
{
a[i] = new double[size];
b[i] = new double[size];
product[i] = new double[size];
}
And don't forget to free
those afterwards, unless you're willing to use shared_ptr or shared_array . 并且不要忘了以后
free
它们,除非您愿意使用shared_ptr或shared_array 。
I wouldn't publish two versions of matrixMultiply
. 我不会发布
matrixMultiply
两个版本。 Delete matrixMultiply
and use only matrixMultiplyThreaded
(which should be renamed, then). 删除
matrixMultiply
并仅使用matrixMultiplyThreaded
(然后应重命名)。 If you reaaaaally want to expose a matrixMultiply
without the dim parameters, code in in terms of matrixMultiplyThreaded
: 如果您reaaaaally要公开一个
matrixMultiply
中的条款,而不昏暗的参数,代码matrixMultiplyThreaded
:
static void matrixMultiply(double** a, double** b, double** product, int size) {
matrixMultiplyThreaded(a, b, product, 0, size, size);
}
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