1 / 5

Understanding MPI_Bcast: Broadcasting Data in Parallel Computing

MPI_Bcast is a core function in the Message Passing Interface (MPI), utilized for broadcasting data from one process to all other processes in a communicator. The syntax is MPI_Bcast(&msg_address, #_elements, MPI_Type, ID, Communicator). For instance, MPI_Bcast(&k, 1, MPI_INT, 0, MPI_COMM_WORLD) sends the value of k from process 0 to all other processes. This function is crucial when data updates need to be shared across processes. Proper placement of MPI_Bcast is essential to avoid blocking issues. A simple program demonstrates its functionality in a parallel computing scenario.

ahmed-johnson
Download Presentation

Understanding MPI_Bcast: Broadcasting Data in Parallel Computing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MPI_Bcast • Bcast stands for broadcast, and is used to send data from one process to all other processes. • The format for this function is: MPI_Bcast(&msg_address,#_elements,MPI_Type, ID, Communicator). • MPI_Bcast (&k, 1, MPI_INT, 0, MPI_COMM_WORLD) • Process 0 sends k to all other processes

  2. MPI_Bcast • This function is best used when a some data that a process was using is changed, and it needs to get updated by all other processes in that communicator (ie: the next homework). • Note: A call to MPI_Bcast must be placed where all processes can see it, if not the sending process will block and hang, waiting for an acknowledgement.

  3. Data Empty Write data to all processes Data Empty Data Empty Data written, unblock Data Present Data Present Data Present MPI_Bcast Process 1 Process 2 Process 3 Process 0 Data Present

  4. Simple Program that Demonstrates MPI_Bcast: #include <mpi.h> #include <stdio.h> int main (int argc, char *argv[]){ int k,id,p,size; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD, &id); MPI_Comm_size(MPI_COMM_WORLD, &size); if(id == 0) k = 20; else k = 10; for(p=0; p<size; p++){ if(id == p) printf("Process %d: k= %d before\n",id,k); } //note MPI_Bcast must be put where all other processes //can see it. MPI_Bcast(&k,1,MPI_INT,0,MPI_COMM_WORLD); for(p=0; p<size; p++){ if(id == p) printf("Process %d: k= %d after\n",id,k); } MPI_Finalize(); return 0

  5. The Output would look like: Process 0: k= 20 before Process 0: k= 20 after Process 3: k= 10 before Process 3: k= 20 after Process 2: k= 10 before Process 2: k= 20 after Process 1: k= 10 before Process 1: k= 20 after

More Related