Re: [OMPI users] Regarding the execution time calculation

True. I was curious as to what happens when I am time sharing the CPU. -- Sent from my iPhone On May 8, 2012, at 3:11 AM, TERRY DONTJE wrote: > On 5/7/2012 8:40 PM, Jeff Squyres (jsquyres) wrote: >> >> On May 7, 2012, at 8:31 PM, Jingcha Joba wrote: >> >>> So in the

Re: [OMPI users] Regarding the execution time calculation

On 5/7/2012 8:40 PM, Jeff Squyres (jsquyres) wrote: On May 7, 2012, at 8:31 PM, Jingcha Joba wrote: So in the above stated example, end-start will be: + 20ms ? (time slice of P2 + P3 = 20ms) More or less (there's nonzero amount of time required for the kernel scheduler, and the time

Re: [OMPI users] Regarding the execution time calculation

Jeff, So in the above stated example, end-start will be: + 20ms ? (time slice of P2 + P3 = 20ms) On Mon, May 7, 2012 at 1:42 PM, Jeff Squyres (jsquyres) wrote: > On May 7, 2012, at 2:39 PM, Jingcha Joba wrote: > > > OK.This explains that if a process gets "migrated" from

Re: [OMPI users] Regarding the execution time calculation

On May 7, 2012, at 2:39 PM, Jingcha Joba wrote: > OK.This explains that if a process gets "migrated" from one CPU to another, > the time is not "affected". But it still doesn't explain if the process gets > scheduled back to the same CPU. MPI_Wtime() doesn't tell you any of this stuff. It

Re: [OMPI users] Regarding the execution time calculation

OK.This explains that if a process gets "migrated" from one CPU to another, the time is not "affected". But it still doesn't explain if the process gets scheduled back to the same CPU. Just in case I have not explained my question clearly, let me explain it from the schedular's perspective. Lets

Re: [OMPI users] Regarding the execution time calculation

MPI_Wtime() returns the elapsed time since some arbitrary time in the past. It is a measure of "wallclock" time, not of CPU time or anything. On 5/4/2012 3:08 PM, Jingcha Joba wrote: Lets say I have a code like this start = MPI_Wtime() stop = MPI_Wtime(); What happens when right after

Re: [OMPI users] Regarding the execution time calculation

Lets say I have a code like this start = MPI_Wtime() stop = MPI_Wtime(); What happens when right after start=MPI_Wtime(), the timeslice of the process ( from the operating system's perspective not the MPI process) is over, and the operating system schedules a next process, after saving the

Re: [OMPI users] Regarding the execution time calculation

A few nodes: 1. I think you posted an incorrect version of your code -- it's calling MPI_Test on an uninitialized request. 2. This looks like a homework problem. I try very hard not to do peoples' homework. :-) My first comment to you stands: you need to be more fine-grained in your timing

Re: [OMPI users] Regarding the execution time calculation

Hi, I haven't used the more mpi process also but still am still unable to reduce my exection time.Here is my code *http://seshendramln.blogspot.se/* and please help me in solving. In this code iam getting the same execution time in i increase or decrease the no.of nodes. thanking you With

Re: [OMPI users] Regarding the execution time calculation

You probably need to be more fine-grained in your timing. Find out exactly what is increasing in time. This is a common symptom for codes that do not scale well -- i.e., adding more MPI processes actually causes it to slow down. On May 3, 2012, at 7:48 AM, seshendra seshu wrote: > Hi, > I

Re: [OMPI users] Regarding the execution time calculation

On May 3, 2012, at 2:02 PM, Jingcha Joba wrote: > Not related to this question , but just curious, is Wtime context switch safe > ? Not sure exactly what you're asking here...? -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to:

Re: [OMPI users] Regarding the execution time calculation

Not related to this question , but just curious, is Wtime context switch safe ? -- Sent from my iPhone On May 3, 2012, at 4:48 AM, seshendra seshu wrote: > Hi, > I have written an parallel program and when i run my program on 4,8,16 nodes > and calculated the execution

Re: [OMPI users] Regarding the execution time calculation

Hi, could you also attach your current code ? Regards Björn From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] On Behalf Of seshendra seshu Sent: den 3 maj 2012 13:49 To: Open MPI Users Subject: [OMPI users] Regarding the execution time calculation Hi, I have written