Hello, i need help regarding a mpi program which solves the 2d heat equation. I have rewritten the original code in my own way, in oder to understand well the parallelization.
I will initially make it work with 4 processors (nproc=4) with a 2D domain of 100 points, that is to say 10 on the x axis (size_x=10) and 10 on the y axis (size_y=10). The 2D is divided into four (x_domains=2 and y_domains=2). The array of values ( "x0 in the code ) has a dimension of 8 * 8, so each processor works on 4 * 4 arrays. The current process rank is stored in "me". I calculate the coordinates of the domain interval for each worker : xdeb(me)<x<xfin(me) and ydeb(me)<y<yfin(me) for "me" process. I check it and it's correct. The initial conditions like x_domains,y_domains,size_x, size_y, the max step, the tolerance, are stored in param<ftp://toulouse-immobilier.bz/pub/param>file. There are a total of three main files : the main program explicitPar.f90<ftp://toulouse-immobilier.bz/pub/explicitPar.f90>which does initialization, calls in the main loop : the explitUtil solving routine in explUtil.f90<ftp://toulouse-immobilier.bz/pub/explUtil.f90>and updates the neighbors of the current process with updateBound routine in updateBound.f90<ftp://toulouse-immobilier.bz/pub/updateBound.f90>. Everything seems ok except the "updateBound" routine : I have a problem with the indexes of row and columns in the communication between North Neighbors, South Neighbors, West and East Neighbors. For example, I have : ------------------------------------------------------------------------------------------------------------ ! Send my boundary to North and receive from South CALL MPI_SENDRECV(x(ydeb(me),xdeb(me)), 1, row_type ,neighBor(N),flag, & x(yfin(me),xdeb(me)), 1, row_type,neighbor(S),flag, & comm2d, status, infompi) ------------------------------------------------------------------------------------------------------------ For 4 processors and me=0, i have : xdeb(0)=1 xfin(0)=4 ydeb(0)=5 yfin(0 )=8 So I send to the North neighbor the upper row indexed by x(ydeb(me),xdeb(me)). But I should have ghost cells for the communication in this case for calculting the next values of "x0" array for each worker. Actually I need the boundaries values for each worker ( with 4*4 size) but I think I have to work on a 5*5 size for this calculation in order to have ghost cells on the edges of 4*4 worker cells. You can compile this code by adapting the makefile<ftp://toulouse-immobilier.bz/pub/makefile>with :" $ make explicitPar " and execute it in my case with : "$ mpirun -n 4 explicitPar " Anyone could see what's wrong with my code ? Have I got to put a 12*12 size for the global domain ? it would allow to have 5*5 worker cells with 2 more for the boundary condition (constant), so a total equal to 12 for size_x and size_y ( 8+2+2). Note that the edges of the domain remain equal to 10 as it's expected. Any help would be really appreciated. Thanks in advance.
