[MPICH] Response too slow! running "mpiexec -n 5 cpi"

[Syed Irfan]

Hi,

Could you try it without fflush(stderr), as fprintf(stderr, ...) is a
non-buffered stream, fflush(stderr) is unnecessary. OTH you could also
fprintf(FILE *, ....) on the master and see if writing to file takes the
same amount of time? Lastly you could run jumpshot and see whats
happening with your program, and build mpich with debug.

hth,
Irfan


章少衡 wrote:

>hello, Rusty
>Thanks for your comments.
>i do some tests as shown below:
>
>1.
>The followings were the execution time for each command:
>
>    mpdboot -n 8 -f myhosts       -------> 2 seconds
>    mpdtrace -l                   -------> instantaneous 
>    mpdringtest                   -------> less than a second
>
>The response to mpdringtest was
>    "time for 1 loops = 0.00226........ seconds"
>2.
>Another program was tested to estimate the network transmission speed.  I "think" the speed was
>almost 450M Bits/second: 450000000 Bits per second=8(bits per byte)*4(bytes per
>double)*2000000(size in double)*50(rounds)*2(transmitting times per broadcast)/13.649424(seconds)
>
>The running results:
>[.....]$ mpiexec -n 4 mytestcodes   
>w    ----> 'w' was output 1 seconds after the command keyed in                                   
>w
>w
>w
>0
>1
>3
>2
>wall clock time = 13.649424
>wall clock time = 13.814960
>
>[.....]$ mpiexec -n 8 mytestcodes
>w    --------> response very slowly
>w
>w
>w
>w
>w
>w
>w
>0
>1
>2
>3
>5
>6
>4
>7
>wall clock time = 19.470830
>wall clock time = 20.812201
>
>
>The followings were the codes:
>
>#include <mpi.h>
>#include <math.h>            
>#include <stdio.h>
>#include <stdlib.h>
>#include <string.h>
>int myid;
>#define LLL 2000000
>double lotus[LLL];
>char processor_name[32];
>int main(int argc, char *argv[])
>{
>	int numprocs,merror;
>	int  namelen;
>
>	//MPI=====================================================================================	
>	fprintf(stderr,"w\n");
>	fflush(stderr);
>	merror=MPI_Init(&argc,&argv);
>	if(merror!=0)
>	{
>		printf("Error intializing MPI program. Terminating.\n");
>		MPI_Abort(MPI_COMM_WORLD,merror);
>		MPI_Finalize();
>		return -1;
>	}
>
>	MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
>	//nodemax=numprocs-1;///////////////////////////
>	MPI_Comm_rank(MPI_COMM_WORLD,&myid);
>	MPI_Get_processor_name(processor_name,&namelen);
>	fprintf(stderr,"%d\n",myid);
>	fflush(stderr);
>
>	double startwtime;
>	if(myid==0)
>		 startwtime= MPI_Wtime();
>
>	for(int asd=0;asd<50;asd++)
>	MPI_Bcast(lotus,LLL,MPI_DOUBLE,0,MPI_COMM_WORLD);
>
>	double endwtime;
>	if(myid==0)
>	{
>		endwtime = MPI_Wtime();
>		printf("wall clock time = %f\n",endwtime-startwtime);
>	}
>	
>	if(myid==0)
>		 startwtime= MPI_Wtime();
>
>	for( asd=0;asd<50;asd++)
>	MPI_Bcast(lotus,LLL,MPI_DOUBLE,numprocs-1,MPI_COMM_WORLD);
>	if(myid==0)
>	{
>		endwtime = MPI_Wtime();
>		printf("wall clock time = %f\n",endwtime-startwtime);
>	}
>	
>	MPI_Finalize();
>	return 0;
>
>}
>
>Thanks for your patience!
>
>
>--- Rusty Lusk <lusk at mcs.anl.gov> wrote:
>
>  
>
>>That is unusually slow.  I would expect it to take less than a second.
>>How long does it take to do mpdtrace?  You can time how long it takes
>>for a message to traverse the mpd ring with mpdringtest.  Use the -help
>>argument for each of these commands to find out more about them.
>>
>>Rusty Lusk
>>
>>From: 章少衡 <shc1515 at yahoo.com.tw>
>>Subject: [MPICH] Response too slow! running "mpiexec -n 5 cpi"
>>Date: Sun, 13 Aug 2006 18:53:41 +0800 (CST)
>>
>>    
>>
>>>Is it a normal operation?
>>>
>>>After input the command
>>>mpiexec -n 5 cpi
>>>
>>>it took almost 22 seconds to show the response 
>>>"
>>>Process 0 of 5 on server
>>>Process 1 of 5 on c2
>>>Process 2 of 5 on c4
>>>Process 3 of 5 on c3
>>>Process 4 of 5 on c1
>>>.....
>>>wall clock time = 0.005223
>>>"
>>>
>>>Is it normal?
>>>
>>>here is my system:
>>>
>>>3Com Baseline 10/100/1000 Switch 8-Port #3C16477
>>>AMD Athlon 64 4000+
>>>NVIDIA GeForce&#8482;6100 GPU + nForce&#8482;430 MCP
>>>
>>>      
>>>
>
>
>
>
>
>
>		
>_________________________________________________________ 
>捇誥轎煤G蚘眊ㄜ笢弊郔Ч轎煤滅馮毀嶼僵閉湮蚘眊 
>http://cn.mail.yahoo.com/?id=77072 
>
>  
>