Databases
StackOverflow2013
Postsdbo
POOpenMPI doesn't send data from an array
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POOpenMPI doesn't send data from an array
    primarykey
    data
    text
    <p>I am trying to parallelize a grayscale filter for BMP image, my function get stuck when trying to send data from a pixel array.</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;time.h&gt; #include "mpi.h" #define MASTER_TO_SLAVE_TAG 1 //tag for messages sent from master to slaves #define SLAVE_TO_MASTER_TAG 10 //tag for messages sent from slaves to master #pragma pack(1) struct image { struct fileHeader fh; struct imageHeader ih; pixel *array; }; struct fileHeader { //blablabla... }; struct imageHeader { //blablabla... }; typedef struct { unsigned char R; unsigned char G; unsigned char B; }pixel; void grayScale_Parallel(struct image *im, int size, int rank) { int i,j,lum,aux,r; pixel tmp; int total_pixels = (*im).ih.width * (*im).ih.height; int qty = total_pixels/(size-1); int rest = total_pixels % (size-1); MPI_Status status; //printf("\n%d\n", rank); if(rank == 0) { for(i=1; i&lt;size; i++){ j = i*qty - qty; aux = j; if(rest != 0 &amp;&amp; i==size-1) {qty=qty+rest;} //para distrubuir toda la carga printf("\nj: %d qty: %d rest: %d\n", j, qty, rest); //it gets stuck here,it doesn't send the data MPI_Send(&amp;(*im).array[j], qty*3, MPI_BYTE, i, MASTER_TO_SLAVE_TAG, MPI_COMM_WORLD); MPI_Send(&amp;aux, 1, MPI_INT, i, MASTER_TO_SLAVE_TAG+1, MPI_COMM_WORLD); MPI_Send(&amp;qty, 1, MPI_INT, i, MASTER_TO_SLAVE_TAG+2, MPI_COMM_WORLD); printf("\nSending to node=%d, sender node=%d\n", i, rank); } } else { MPI_Recv(&amp;aux, 1, MPI_INT, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG+1, MPI_COMM_WORLD,&amp;status); MPI_Recv(&amp;qty, 1, MPI_INT, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG+2, MPI_COMM_WORLD,&amp;status); pixel *arreglo = (pixel *)calloc(qty, sizeof(pixel)); MPI_Recv(&amp;arreglo[0], qty*3, MPI_BYTE, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG, MPI_COMM_WORLD,&amp;status); //PROCESS RECEIVED PIXELS... //SEND to ROOT PROCESS } if (rank==0){ //RECEIVE DATA FROM ALL PROCESS } } int main(int argc, char *argv[]) { int rank, size; MPI_Init(&amp;argc, &amp;argv); MPI_Comm_size(MPI_COMM_WORLD, &amp;size); MPI_Comm_rank(MPI_COMM_WORLD, &amp;rank); MPI_Status status; int op=1; char filename_toload[50]; int bright_number=0; struct image image2; if (rank==0) { printf("File to load: \n"); scanf("%s", filename_toload); loadImage(&amp;image2, filename_toload); } while(op != 0) { if (rank==0) { printf("Welcome to example program!\n\n"); printf("\t1.- GrayScale Parallel Function\n"); printf("\t2.- Call another Function\n"); printf("\t0.- Exit\n\t"); printf("\n\n\tEnter option:"); scanf("%d", &amp;op); } //Broadcast the user's choice to all other ranks MPI_Bcast(&amp;op, 1, MPI_INT, 0, MPI_COMM_WORLD); switch(op) { case 1: grayScale_Parallel(&amp;image2, size, rank); MPI_Barrier(MPI_COMM_WORLD); printf("GrayScale applied successfully!\n\n"); break; case 2: function_blabla(); printf("Function called successfully\n\n"); break; } } MPI_Finalize(); return 0; } </code></pre> <p>I think the MPI_Send function can't read the array of pixels, but is strange because i can print the pixels.</p> <p>Any idea?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USBenjamin
    1. USJohn Smith
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COYou seem to be hiding pertinent information in your //blablabla from the first else of your grayScale_Parallel function. I see your MPI_Send functions, which are blocking waiting for their MPI_Recv counterpart, which you haven't shown.
      singulars
      1. POOpenMPI doesn't send data from an array
      1. USSoravux
    2. COBut almost with the above code it should send the data to the ith process.
      singulars
      1. POOpenMPI doesn't send data from an array
      1. USJohn Smith
    3. COMPI_Send is blocking. It will only send when the process is executing MPI_Recv. Asynchronous versions of these functions are MPI_Isend and MPI_Irecv. Without your MPI_Recv calls, we can't help you further.
      singulars
      1. POOpenMPI doesn't send data from an array
      1. USSoravux
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload