George,
I am using each host with 4 interfaces including loopback interface. Can you
please let me know more about your environment?
eth0 Link encap:Ethernet HWaddr bc:30:5b:db:ae:6f
inet addr:xxx.xxx.xxx.134 Bcast:xxx.xxx.xxx.255 Mask:255.255.255.0
inet6 addr: fe80::be30:5bff:fedb:ae6f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1375598 errors:0 dropped:0 overruns:0 frame:0
TX packets:709644 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1431654357 (1.4 GB) TX bytes:69604165 (69.6 MB)
Interrupt:17
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:944 errors:0 dropped:0 overruns:0 frame:0
TX packets:944 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:264692 (264.6 KB) TX bytes:264692 (264.6 KB)
vmnet1 Link encap:Ethernet HWaddr 00:50:56:c0:00:01
inet addr: xxx.xxx.xxx.1 Bcast: xxx.xxx.xxx.255 Mask:255.255.255.0
inet6 addr: fe80::250:56ff:fec0:1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:245 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
vmnet8 Link encap:Ethernet HWaddr 00:50:56:c0:00:08
inet addr: xxx.xxx.xxx..1 Bcast: xxx.xxx.xxx..255 Mask:255.255.255.0
inet6 addr: fe80::250:56ff:fec0:8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:58357 errors:0 dropped:0 overruns:0 frame:0
TX packets:238 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
From: devel-boun...@open-mpi.org [mailto:devel-boun...@open-mpi.org] On Behalf
Of George Bosilca
Sent: Wednesday, October 10, 2012 4:41 AM
To: Open MPI Developers
Subject: Re: [OMPI devel] MPI_Reduce Hangs in my Application
Your code works for me on two platforms. Thus, I guess the problem is with the
communication layer (BTL) is Open MPI. What network do you use? If Ethernet how
many interfaces?
Thanks,
george.
On Oct 10, 2012, at 09:30 , Santhosh Kokala
<santhosh.kok...@riverbed.com<mailto:santhosh.kok...@riverbed.com>> wrote:
I have a problem with my MPI code, it hangs when the code is run on multiple
nodes. It successfullycompletes when run on a single node. I am not sure how to
debug this. Can someone help me debug this issue?
Program Usage:
mpicc -o string string.cpp
mpirun -np 4 -npernode 2 -hostfile hosts ./string 12 0.1 0.9 10 2
MPI_Reduce Hangs in 2nd iteration: (Output cout statements from my program)
1st Iteration (Timestep 1)
-----------------------------------------------------
0 Waiting for MPI_Reduce()
0 Done Waiting for MPI_Reduce()
1 Waiting for MPI_Reduce()
1 Done Waiting for MPI_Reduce()
2 Waiting for MPI_Reduce()
2 Done Waiting for MPI_Reduce()
3 Waiting for MPI_Reduce()
3 Done Waiting for MPI_Reduce()
0 Sending to right task = 1
0 Receiving from right task = 1
1 Receiving from left task = 0
1 Sending to left task = 0
1 Sending to right task = 2
1 Receiving from right task = 2
2 Receiving from left task = 1
2 Sending to left task = 1
2 Sending to right task = 3
2 Receiving from right task = 3
3 Receiving from left task = 2
3 Sending to left task = 2
2nd Iteration (Timestep 2)
-----------------------------------------------------
0 Waiting for MPI_Reduce()
1 Waiting for MPI_Reduce()
1 Done Waiting for MPI_Reduce()
2 Waiting for MPI_Reduce()
3 Waiting for MPI_Reduce()
My Code:
#include <iostream>
#include <vector>
#include <stdio.h>
#include <stdlib.h>
#include "mpi.h"
#define MASTER 0
int RtoL = 10;
int LtoR = 20;
int main ( int argc, char **argv )
{
int nprocs, taskid;
FILE *f = NULL;
int left, right, i_start, i_end;
float sum = 0;
MPI_Status status;
float *y, *yold;
float *v, *vold;
// const int NUM_MASSES = 1000;
// const float Ktension = 0.1;
// const float Kdamping = 0.9;
// const float duration = 10.0;
#if 0
if ( argc != 5 ) {
std::cout << "usage: " << argv[0] << " NUM_MASSES durationInSecs
Ktension Kdamping\n";
return 2;
}
#endif
int NUM_MASSES = atoi ( argv[1] );
float duration = atof ( argv[2] );
float Ktension = atof ( argv[3] );
float Kdamping = atof ( argv[4] );
const int PICKUP_POS = NUM_MASSES / 7;
const int OVERSAMPLING = 16;
MPI_Init(&argc,&argv);
MPI_Comm_size(MPI_COMM_WORLD,&nprocs);
MPI_Comm_rank(MPI_COMM_WORLD,&taskid);
if (taskid == 0) {
f = fopen ( "rstring.raw", "wb" );
if (!f) {
std::cout << "can't open output file\n";
return 1;
}
}
y = new float[NUM_MASSES];
yold = new float[NUM_MASSES];
v = new float[NUM_MASSES];
for (int i = 0; i < NUM_MASSES; i++ ) {
v[i] = 0.0f;
yold[i] = y[i] = 0.0f;
if (i == NUM_MASSES/2 )
yold[i] = 1.0;
}
if (taskid == 0) {
left = -1;
right = 1;
} else if (taskid == nprocs - 1) {
left = taskid - 1;
right = -1;
} else {
left = taskid - 1;
right = taskid + 1;
}
i_start = taskid * (NUM_MASSES/nprocs);
i_end = i_start + (NUM_MASSES/nprocs);
int numIters = duration * 44100 * OVERSAMPLING;;
if (argc == 6) {
numIters = atoi(argv[5]);
}
for ( int t = 0; t < numIters; t++ ) {
float sum = 0;
float gsum = 0;
for ( int i = i_start; i < i_end; i++ ) {
if ( i == 0 || i == NUM_MASSES-1 ) {
} else {
float accel = Ktension * (yold[i+1] + yold[i-1] - 2*yold[i]);
v[i] += accel;
v[i] *= Kdamping;
y[i] = yold[i] + v[i];
sum += y[i];
}
}
std::cout << taskid << " Waiting for MPI_Reduce()" << std::endl;
MPI_Reduce(&sum, &gsum, 1, MPI_FLOAT, MPI_SUM, MASTER, MPI_COMM_WORLD);
std::cout << taskid << " Done Waiting for MPI_Reduce()" << std::endl;
if (taskid != 0) {
MPI_Recv(&y[i_start-1], 1, MPI_FLOAT, left, LtoR, MPI_COMM_WORLD,
&status);
std::cout << taskid << " Receiving from left task = " << left <<
std::endl;
MPI_Send(&y[i_start], 1, MPI_FLOAT, left, RtoL, MPI_COMM_WORLD);
std::cout << taskid << " Sending to left task = " << left <<
std::endl;
}
if (taskid != nprocs - 1) {
MPI_Send(&y[i_end-1],1, MPI_FLOAT, right, LtoR, MPI_COMM_WORLD);
std::cout << taskid <<" Sending to right task = " << right <<
std::endl;
MPI_Recv(&y[i_end], 1, MPI_FLOAT, right, RtoL, MPI_COMM_WORLD,
&status);
std::cout << taskid <<" Receiving from right task = " << right <<
std::endl;
}
//printf("After Reduce task = %d yold = %f %f %f %f\n", taskid,yold[0],
yold[1], yold[2], yold[3]);
//printf("After Reduce task = %d y = %f %f %f %f\n", taskid, y[0],
y[1], y[2], y[3]);
//printf("After Reduce task = %d v = %f %f %f %f\n", taskid, v[0],
v[1], v[2], v[3]);
float *tmp = y;
y = yold;
yold = tmp;
if (taskid == 0) {
//std::cout<< "sum = " << gsum << std::endl;
if ( t % OVERSAMPLING == 0 ) {
fwrite ( &gsum, sizeof(float), 1, f );
}
}
}
if (taskid == 0) {
fclose ( f );
}
MPI_Finalize();
}
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