Hi Christian, The code you posted is very similar to another school assignment sent to this list 2 years ago:
http://www.open-mpi.org/community/lists/users/2010/10/14619.php At that time, the code was written in Fortran, and now it is written in C - however, the variable names, logic, etc are quite similar! :-D Remember, debugging and bug fix is part of the (home) work! Rayson ================================================== Open Grid Scheduler - The Official Open Source Grid Engine http://gridscheduler.sourceforge.net/ On Sun, Aug 19, 2012 at 12:59 AM, Christian Perrier <christian01.perr...@gmail.com> wrote: > Hi, > > I have a problem with MPI_Senrecv communication where I send columns on > edges between processes. > For debugging, I show you below a basic example where I initialize a 10x10 > matrix ("x0" array) with x_domain=4 > and y_domain=4. For the test, I simply initialize the 2D array values with > x0[i][j] = i+j . After, in updateBound.c", I'm > using the MPI_Sendrecv functions for the North-South and Est-West process. > > Here's the main program "example.c" : > > ------------------------------------------------------------------------------------------- > > #include <stdio.h> > #include <stdlib.h> > #include <math.h> > #include "mpi.h" > > int main(int argc, char *argv[]) > { > /* size of the discretization */ > > double** x; > double** x0; > > int i,j,k,l; > int nproc; > int ndims; > int S=0, E=1, N=2, W=3; > int NeighBor[4]; > int xcell, ycell, size_tot_x, size_tot_y; > int *xs,*ys,*xe,*ye; > int size_x = 4; > int size_y = 4; > int me; > int x_domains=2; > int y_domains=2; > > MPI_Comm comm, comm2d; > int dims[2]; > int periods[2]; > int reorganisation = 0; > int row; > MPI_Datatype column_type; > > > > size_tot_x=size_x+2*x_domains+2; > size_tot_y=size_y+2*y_domains+2; > > xcell=(size_x/x_domains); > ycell=(size_y/y_domains); > > MPI_Init(&argc, &argv); > comm = MPI_COMM_WORLD; > MPI_Comm_size(comm,&nproc); > MPI_Comm_rank(comm,&me); > > x = malloc(size_tot_y*sizeof(double*)); > x0 = malloc(size_tot_y*sizeof(double*)); > > > for(j=0;j<=size_tot_y-1;j++) { > x[j] = malloc(size_tot_x*sizeof(double)); > x0[j] = malloc(size_tot_x*sizeof(double)); > } > > xs = malloc(nproc*sizeof(int)); > xe = malloc(nproc*sizeof(int)); > ys = malloc(nproc*sizeof(int)); > ye = malloc(nproc*sizeof(int)); > > /* Create 2D cartesian grid */ > periods[0] = 0; > periods[1] = 0; > > ndims = 2; > dims[0]=x_domains; > dims[1]=y_domains; > > MPI_Cart_create(comm, ndims, dims, periods, reorganisation, &comm2d); > > /* Identify neighbors */ > > NeighBor[0] = MPI_PROC_NULL; > NeighBor[1] = MPI_PROC_NULL; > NeighBor[2] = MPI_PROC_NULL; > NeighBor[3] = MPI_PROC_NULL; > > /* Left/West and right/Est neigbors */ > > MPI_Cart_shift(comm2d,0,1,&NeighBor[W],&NeighBor[E]); > > /* Bottom/South and Upper/North neigbors */ > > MPI_Cart_shift(comm2d,1,1,&NeighBor[S],&NeighBor[N]); > > /* coordinates of current cell with me rank */ > > xcell=(size_x/x_domains); > ycell=(size_y/y_domains); > > ys[me]=(y_domains-me%(y_domains)-1)*(ycell+2)+2; > ye[me]=ys[me]+ycell-1; > > for(i=0;i<=y_domains-1;i++) > {xs[i]=2;} > > for(i=0;i<=y_domains-1;i++) > {xe[i]=xs[i]+xcell-1;} > > for(i=1;i<=(x_domains-1);i++) > { for(j=0;j<=(y_domains-1);j++) > { > xs[i*y_domains+j]=xs[(i-1)*y_domains+j]+xcell+2; > xe[i*y_domains+j]=xs[i*y_domains+j]+xcell-1; > } > } > > for(i=0;i<=size_tot_y-1;i++) > { for(j=0;j<=size_tot_x-1;j++) > { x0[i][j]= i+j; > // printf("%f\n",x0[i][j]); > } > } > > /* Create column data type to communicate with South and North > neighbors */ > > MPI_Type_vector( ycell, 1, size_tot_x, MPI_DOUBLE, &column_type); > MPI_Type_commit(&column_type); > > updateBound(x0, NeighBor, comm2d, column_type, me, xs, ys, xe, ye, > xcell); > > > for(i=0;i<=size_tot_y-1;i++) > { > free(x[i]); > free(x0[i]); > } > > free(x); > free(x0); > > free(xs); > free(xe); > free(ys); > free(ye); > > MPI_Finalize(); > > return 0; > } > ------------------------------------------------------------------------------------------- > > and the second file "updateBound.c" which sends the columns and rows > > > ------------------------------------------------------------------------------------------- > > > #include "mpi.h" > #include <stdio.h> > > /*******************************************************************/ > /* Update Bounds of subdomain with me process */ > /*******************************************************************/ > > void updateBound(double** x,int NeighBor[], MPI_Comm comm2d, MPI_Datatype > column_type , int me, int* xs, int* ys, int* xe, int* ye, int xcell) > { > > int S=0, E=1, N=2, W=3; > int flag; > MPI_Status status; > > int i,j; > > if(me==0) {printf("verif_update_before\n"); > for(i=ys[me]-1;i<=ye[me]+1;i++) > { for(j=xs[me]-1;j<=xe[me]+1;j++) > { printf("%f ",x[i][j]); > } > printf("\n"); > } > printf("\n"); > } > > /********* North/South communication **********************************/ > flag = 1; > /*Send my boundary to North and receive from South*/ > MPI_Sendrecv(&x[ys[me]][xs[me]], xcell, MPI_DOUBLE, NeighBor[N], flag, > &x[ye[me]+1][xs[me]], xcell, MPI_DOUBLE, NeighBor[S], flag, comm2d, > &status); > > /*Send my boundary to South and receive from North*/ > MPI_Sendrecv(&x[ye[me]][xs[me]], xcell, MPI_DOUBLE, NeighBor[S], flag, > &x[ys[me]-1][xs[me]], xcell, MPI_DOUBLE, NeighBor[N], flag, comm2d, > &status); > > /********* Est/West communication ************************************/ > flag = 2; > /*Send my boundary to Est and receive from West*/ > MPI_Sendrecv(&x[ys[me]][xe[me]], 1, column_type, NeighBor[E], flag, > &x[ys[me]][xs[me]-1], 1, column_type, NeighBor[W], flag, comm2d, &status); > > /*Send my boundary to West and receive from Est*/ > MPI_Sendrecv(&x[ys[me]][xs[me]], 1, column_type, NeighBor[W], flag, > &x[ys[me]][xe[me]+1], 1, column_type, NeighBor[E], flag, comm2d, &status); > > if(me==0) {printf("verif_update_after\n"); > for(i=ys[me]-1;i<=ye[me]+1;i++) > { for(j=xs[me]-1;j<=xe[me]+1;j++) > { printf("%f ",x[i][j]); > } > printf("\n"); > } > printf("\n"); > } > } > > ------------------------------------------------------------------------------ > > Running with nproc=4, I print the values of the subarray with rank=0 (so at > left bottom of the grid) and I get before and after the > bounds udpate : > > verif_update_before > 6.000000 7.000000 8.000000 9.000000 > 7.000000 8.000000 9.000000 10.000000 > 8.000000 9.000000 10.000000 11.000000 > 9.000000 10.000000 11.000000 12.000000 > > verif_update_after > 6.000000 5.000000 6.000000 9.000000 > 7.000000 8.000000 9.000000 12.000000 > 8.000000 9.000000 10.000000 11.000000 > 9.000000 10.000000 11.000000 12.000000 > > As you can see, after the udpate, I don't have the correct value ( in > underligned bold : 11.0 ) at the second element > of the column coming from the Est. I expected 13.0 instead of 11.0. > > So there's a problem with the column datatype which only send the first > element of this column. > > In "example.c", I define the column as following : > > MPI_Type_vector( ycell, 1, size_tot_x, MPI_DOUBLE, &column_type); > MPI_Type_commit(&column_type); > > However, It seems ok and the computation of begin and end coordinates as a > function of rank "me" is also good. > > I make you notice there's no problem between the exchange of rows between > the North and the South, only > between columns. > > If you could help me, I don't know what to do. > > Regards > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users
