hi all,
I have written a DO loop in FORTRAN(making use of MPI)
that calculates the sum of N given numbers(calculates
the sum of 1 to N numbers.).
i hv given N = 5 million and ran the program.
I am making use of 8 uniprocessor homogeneous Linux
machines to test and find the optimal output..
So the test involves :the number of machines being
used ranging from 1 to 8 and the number of processes
ranging from 2 to 80.
I have come to the conclusion that the least time
taken is when the number of processes is equal to the
number of machines ie processors being used.(and time
taken isthe least when maximum number of machines are
being used)
But i was assuming that as the number of processes
increase,the time taken for the calculation
reduces.(cause LAM allows one to spawn several
processes on one machine)..Why doesnt this happen ?
Does it mean that whatever DO loop i might run,i will
get the best output when the number of processes =
number of uniprocessor machines ?
What happens in case of multiprocessors ?
Can someone clarify this ?
I need a reply asap as i hv a submission regarding the
same.
regards,
Vidya Kotamraju
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