梯形积分法
菜包的总结
首次撸OpenMP示例程序，==关键问题在于C语言的语法及基础知识的不足;
其次对于OpenMP编程模型的掌握还不熟练;
知识点
- scanf()输入%lf-->double;%f-->float;%d-->int; …
其中后半部分是&a，不能写变量名称;- openMP 基本块:
-并行部分： # pragma omp parallel ...;
-互斥部分： # pragma omp critical...;
源码：
#include <stdio.h>
#include <stdlib.h>
#include <omp.h>
void Trap(double a,double b,int n,double* res);
double f(double d);
int main(int argc,char* argv[]){
int thread_count = strtol(argv[1],NULL,10);
int n;
double a,b;
double res=0.0;
printf("Please input a, b and n\n");
scanf("%lf,%lf,%d",&a,&b,&n);
printf("a is: %f, b is: %f, n is %d \n ", a,b,n);
# pragma omp parallel num_threads(thread_count)
Trap(a,b,n,&res);
printf("Result is %lf !\n",res);
return 0;
}
void Trap(double a,double b,int n,double* res){
double h,x,my_res;
double local_a,local_b;
int i,local_n;
int rank = omp_get_thread_num();
int thread_count = omp_get_num_threads();
h=(b-a)/n;
local_n = n/thread_count;
local_a = a+h*rank*local_n;
local_b = local_a+local_n*h;
my_res = (f(local_a)+f(local_b))/2.0;
for(i=1;i<local_n;i++){
x = local_a+i*h;
my_res+=f(x);
}
my_res = my_res*h;
# pragma omp critical
*res+=my_res;
}
double f(double d){
return d*d;
}
运行及结果
> gcc -g -Wall -fopenmp -o Tixing Tixing.c
> ./Tixing 5
Please input a, b and n
0.0,10.0,1000
a is: 0.000000, b is: 10.000000, n is 1000
Result is 333.333500 !
