平行計算之梯形積分
阿新 • • 發佈：2019-01-31
方法1
#include<stdio.h> #include"mpi.h" double Trap(double left_endpt,double right_endpt,int trap_count,double base_len); double f(double x); int main(void) { int my_rank,comm_sz,n = 1024,local_n; double a = 0.0, b= 1.0 , h, local_a,local_b; double local_int,total_int; int source; MPI_Init(NULL,NULL); MPI_Comm_rank(MPI_COMM_WORLD,&my_rank); MPI_Comm_size(MPI_COMM_WORLD,&comm_sz); Get_input(my_rank, comm_sz, &a, &b, &n); h = (b-a)/n; local_n= n/comm_sz; local_a = a+my_rank * local_n * h; local_b = local_a + local_n * h; local_int = Trap(local_a ,local_b,local_n,h); if(my_rank!=0) { MPI_Send(&local_int,1,MPI_DOUBLE,0,0,MPI_COMM_WORLD); } else { total_int = local_int; for(source =1; source <comm_sz; source++) { MPI_Recv(&local_int,1,MPI_DOUBLE,source,0,MPI_COMM_WORLD,MPI_STATUS_IGNORE); total_int += local_int; } } if(my_rank == 0) { printf("with n = %d trapezoids, our estimate\n",n); printf("of the integral from %f to %f = %.15e\n",a,b,total_int); } MPI_Finalize(); return 0; } double Trap(double left_endpt,double right_endpt,int trap_count,double base_len) { double estimate,i; int x; estimate = (f(left_endpt) + f(right_endpt))/2.0; for(i = 1; i <= trap_count-1 ; i++) { x = left_endpt + i*base_len; estimate += f(x); } estimate = estimate*base_len; return estimate; } double f(double x) { return 4/(1+x*x); }
VC6執行效果圖
方法2（用到了MPI_Reduce()函式）
#include<stdio.h> #include"mpi.h" double Trap(double left_endpt,double right_endpt,int trap_count,double base_len); double f(double x); int main(void) { int my_rank,comm_sz,n = 1024,local_n; double a = 0.0, b= 1.0 , h, local_a,local_b; double local_int,total_int; int source; MPI_Init(NULL,NULL); MPI_Comm_rank(MPI_COMM_WORLD,&my_rank); MPI_Comm_size(MPI_COMM_WORLD,&comm_sz); h = (b-a)/n; local_n= n/comm_sz; local_a = a+my_rank * local_n * h; local_b = local_a + local_n * h; local_int = Trap(local_a ,local_b,local_n,h); MPI_Reduce(&local_int, &total_int, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);<span style="white-space:pre"> </span>//2 if(my_rank == 0) { printf("with n = %d trapezoids, our estimate\n",n); printf("of the integral from %f to %f = %.15e\n",a,b,total_int); } MPI_Finalize(); return 0; } double Trap(double left_endpt,double right_endpt,int trap_count,double base_len) { double estimate,i; int x; estimate = (f(left_endpt) + f(right_endpt))/2.0; for(i = 1; i <= trap_count-1 ; i++) { x = left_endpt + i*base_len; estimate += f(x); } estimate = estimate*base_len; return estimate; } double f(double x) { return 4/(1+x*x); }
VC6執行效果圖
方法3（用到了MPI_Bcast()函式進行廣播）
#include<stdio.h> #include"mpi.h" double Trap(double left_endpt,double right_endpt,int trap_count,double base_len); double f(double x); void Get_input( //3，用於輸入資料 int my_rank, int comm_sz, double* a_p, double* b_p, double* n_p) { if (my_rank==0) { printf("Enter a, b, and n\n"); scanf("%lf %lf %d", a_p, b_p, n_p); } MPI_Bcast(a_p, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD); MPI_Bcast(b_p, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD); MPI_Bcast(n_p, 1, MPI_INT, 0, MPI_COMM_WORLD); } int main(void) { int my_rank,comm_sz,n = 1024,local_n; double a = 0.0, b= 1.0 , h, local_a,local_b; double local_int,total_int; int source; MPI_Init(NULL,NULL); MPI_Comm_rank(MPI_COMM_WORLD,&my_rank); MPI_Comm_size(MPI_COMM_WORLD,&comm_sz); Get_input(my_rank, comm_sz, &a, &b, &n); h = (b-a)/n; local_n= n/comm_sz; local_a = a+my_rank * local_n * h; local_b = local_a + local_n * h; local_int = Trap(local_a ,local_b,local_n,h); MPI_Reduce(&local_int, &total_int, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD); if(my_rank == 0) { printf("with n = %d trapezoids, our estimate\n",n); printf("of the integral from %f to %f = %.15e\n",a,b,total_int); } MPI_Finalize(); return 0; } double Trap(double left_endpt,double right_endpt,int trap_count,double base_len) { double estimate,i; int x; estimate = (f(left_endpt) + f(right_endpt))/2.0; for(i = 1; i <= trap_count-1 ; i++) { x = left_endpt + i*base_len; estimate += f(x); } estimate = estimate*base_len; return estimate; } double f(double x) { return 4/(1+x*x); }
VC6執行效果圖
MPI執行效果圖
