Difference between revisions of "MPI Hello World"

Jump to navigation Jump to search

MPI Hello World (view source)

Revision as of 01:07, 21 December 2022

5,632 bytes added ,  01:07, 21 December 2022
no edit summary
 
(9 intermediate revisions by one other user not shown)
== MPI Hello World ==
 
Many parallel jobs are using [https://en.wikipedia.org/wiki/Message_Passing_Interface MPI] at the lowest level to manage parallel compute resources. You will want to successfully run this example to make sure your parallel computing environment is working properly. These instructions assume you've already set up your cluster ssh keys, as described in [[Cluster SSH access]]
 
This is a 'Hello World' program that will test the operation of sending jobs to remote workers.
int main(int argc, char* argv[])
{
int rank, size, len;
char version[MPI_MAX_LIBRARY_VERSION_STRING];
 
MPI_Init(&argc, &argv);
</nowiki>
 
create a folder and save this file as helloworld_mpi<tt> hello_mpi.c </tt>
 
You can compile this program with
 
mpicc -g helloworld_mpihello_mpi.c -o helloworld_mpihello_mpi
 
You now have an executable called helloworld_mpi<tt> hello_mpi </tt>
 
You can run the command with
 
mpirun ./helloworld_mpi
mpirun ./hello_mpi
 
With no other arguments, mpirun will run all of the tasks on the local machine, usually one for each CPU core. You should see a hello world from each process, on each cpu core.
Now, to run your mpi program on the cluster, you will need to create a hostfile.
First, lets create a simple hostfile that just runs four processes on the local machine
 
 
Put the following line in a file called <tt>localhost </tt>.
 
<nowiki>
</nowiki>
 
Put that line in a file called 'localhost'.
Now run your program with that hostfile, using
 
mpirun --hostfile localhost ./helloworld_mpi
mpirun --hostfile localhost ./hello_mpi
 
<nowiki>
Hello, world, I am 0 of 4
Hello, world, I am 2 of 4
Hello, world, I am 1 of 4
Hello, world, I am 3 of 4
</nowiki>
 
Now create a hostfile called <tt> cluster_hosts </tt> with the following entries:
<nowiki>
pnode01 slots=4 max_slots=8
pnode02 slots=4 max_slots=8
pnode03 slots=4 max_slots=8
pnode04 slots=4 max_slots=8
</nowiki>
 
and keep adding lines until you get to <tt> pnode64 slots=4 max_slots=8 </tt>.
 
The next step assumes you have set up your ssh keys as described in [[Cluster SSH access]]
 
With 64 nodes listed in your <tt> cluster_hosts </tt> file, run your program again with
 
mpirun --hostfile cluster_hosts ./hello_mpi
 
You should see the output shown below, which is 256 lines long, four responses from each host, one for each core described.
 
Once you are able to run this program successfully, your MPI setup is working. This will be necessary before you can run other MPI-based programs, such as ipyparallel programs which use MPI.
 
Note: the example below was run on 40 nodes.
 
<nowiki>
Hello, world, I am 126 of 160
Hello, world, I am 2 of 4, (Open MPI v4.0.3, package: Debian OpenMPI, ident: 4.0.3, repo rev: v4.0.3, Mar 03, 2020, 87)
Hello, world, I am 69 of 160
Hello, world, I am 0 of 4, (Open MPI v4.0.3, package: Debian OpenMPI, ident: 4.0.3, repo rev: v4.0.3, Mar 03, 2020, 87)
Hello, world, I am 159 of 160
Hello, world, I am 1 of 4, (Open MPI v4.0.3, package: Debian OpenMPI, ident: 4.0.3, repo rev: v4.0.3, Mar 03, 2020, 87)
Hello, world, I am 137 of 160
Hello, world, I am 3 of 4, (Open MPI v4.0.3, package: Debian OpenMPI, ident: 4.0.3, repo rev: v4.0.3, Mar 03, 2020, 87)
Hello, world, I am 11 of 160
Hello, world, I am 138 of 160
Hello, world, I am 139 of 160
Hello, world, I am 3 of 160
Hello, world, I am 125 of 160
Hello, world, I am 68 of 160
Hello, world, I am 0 of 160
Hello, world, I am 127 of 160
Hello, world, I am 71 of 160
Hello, world, I am 8 of 160
Hello, world, I am 136 of 160
Hello, world, I am 85 of 160
Hello, world, I am 2 of 160
Hello, world, I am 124 of 160
Hello, world, I am 70 of 160
Hello, world, I am 51 of 160
Hello, world, I am 9 of 160
Hello, world, I am 86 of 160
Hello, world, I am 21 of 160
Hello, world, I am 1 of 160
Hello, world, I am 25 of 160
Hello, world, I am 143 of 160
Hello, world, I am 119 of 160
Hello, world, I am 6 of 160
Hello, world, I am 10 of 160
Hello, world, I am 84 of 160
Hello, world, I am 133 of 160
Hello, world, I am 156 of 160
Hello, world, I am 23 of 160
Hello, world, I am 100 of 160
Hello, world, I am 146 of 160
Hello, world, I am 27 of 160
Hello, world, I am 118 of 160
Hello, world, I am 55 of 160
Hello, world, I am 32 of 160
Hello, world, I am 123 of 160
Hello, world, I am 67 of 160
Hello, world, I am 87 of 160
Hello, world, I am 135 of 160
Hello, world, I am 157 of 160
Hello, world, I am 20 of 160
Hello, world, I am 130 of 160
Hello, world, I am 120 of 160
Hello, world, I am 12 of 160
Hello, world, I am 82 of 160
Hello, world, I am 48 of 160
Hello, world, I am 132 of 160
Hello, world, I am 158 of 160
Hello, world, I am 22 of 160
Hello, world, I am 131 of 160
Hello, world, I am 101 of 160
Hello, world, I am 145 of 160
Hello, world, I am 24 of 160
Hello, world, I am 140 of 160
Hello, world, I am 117 of 160
Hello, world, I am 113 of 160
Hello, world, I am 154 of 160
Hello, world, I am 7 of 160
Hello, world, I am 53 of 160
Hello, world, I am 33 of 160
Hello, world, I am 16 of 160
Hello, world, I am 28 of 160
Hello, world, I am 111 of 160
Hello, world, I am 121 of 160
Hello, world, I am 13 of 160
Hello, world, I am 64 of 160
Hello, world, I am 88 of 160
Hello, world, I am 96 of 160
Hello, world, I am 83 of 160
Hello, world, I am 49 of 160
Hello, world, I am 134 of 160
Hello, world, I am 128 of 160
Hello, world, I am 102 of 160
Hello, world, I am 148 of 160
Hello, world, I am 147 of 160
Hello, world, I am 26 of 160
Hello, world, I am 36 of 160
Hello, world, I am 141 of 160
Hello, world, I am 58 of 160
Hello, world, I am 73 of 160
Hello, world, I am 46 of 160
Hello, world, I am 116 of 160
Hello, world, I am 114 of 160
Hello, world, I am 155 of 160
Hello, world, I am 4 of 160
Hello, world, I am 52 of 160
Hello, world, I am 34 of 160
Hello, world, I am 62 of 160
Hello, world, I am 17 of 160
Hello, world, I am 29 of 160
Hello, world, I am 76 of 160
Hello, world, I am 92 of 160
Hello, world, I am 81 of 160
Hello, world, I am 50 of 160
Hello, world, I am 129 of 160
Hello, world, I am 103 of 160
Hello, world, I am 149 of 160
Hello, world, I am 144 of 160
Hello, world, I am 37 of 160
Hello, world, I am 142 of 160
Hello, world, I am 56 of 160
Hello, world, I am 75 of 160
Hello, world, I am 47 of 160
Hello, world, I am 40 of 160
Hello, world, I am 106 of 160
Hello, world, I am 115 of 160
Hello, world, I am 152 of 160
Hello, world, I am 5 of 160
Hello, world, I am 54 of 160
Hello, world, I am 35 of 160
Hello, world, I am 63 of 160
Hello, world, I am 18 of 160
Hello, world, I am 30 of 160
Hello, world, I am 77 of 160
Hello, world, I am 93 of 160
Hello, world, I am 108 of 160
Hello, world, I am 122 of 160
Hello, world, I am 14 of 160
Hello, world, I am 65 of 160
Hello, world, I am 89 of 160
Hello, world, I am 99 of 160
Hello, world, I am 153 of 160
Hello, world, I am 61 of 160
Hello, world, I am 19 of 160
Hello, world, I am 31 of 160
Hello, world, I am 78 of 160
Hello, world, I am 94 of 160
Hello, world, I am 109 of 160
Hello, world, I am 15 of 160
Hello, world, I am 66 of 160
Hello, world, I am 91 of 160
Hello, world, I am 97 of 160
Hello, world, I am 80 of 160
Hello, world, I am 150 of 160
Hello, world, I am 38 of 160
Hello, world, I am 57 of 160
Hello, world, I am 72 of 160
Hello, world, I am 44 of 160
Hello, world, I am 41 of 160
Hello, world, I am 107 of 160
Hello, world, I am 112 of 160
Hello, world, I am 59 of 160
Hello, world, I am 74 of 160
Hello, world, I am 45 of 160
Hello, world, I am 42 of 160
Hello, world, I am 104 of 160
Hello, world, I am 79 of 160
Hello, world, I am 110 of 160
Hello, world, I am 90 of 160
Hello, world, I am 98 of 160
Hello, world, I am 151 of 160
Hello, world, I am 39 of 160
Hello, world, I am 43 of 160
Hello, world, I am 105 of 160
Hello, world, I am 60 of 160
Hello, world, I am 95 of 160
</nowiki>
Retrieved from "https://e.math.cornell.edu/wiki/index.php/Special:MobileDiff/162...290"

Navigation menu