As I said before, send the -log_summary output for the two processor sizes and we'll look at where it is spending its time and how it could possibly be improved.
Barry > On Feb 28, 2016, at 10:29 AM, TAY wee-beng <[email protected]> wrote: > > > On 27/2/2016 12:53 AM, Barry Smith wrote: >>> On Feb 26, 2016, at 10:27 AM, TAY wee-beng <[email protected]> wrote: >>> >>> >>> On 26/2/2016 11:32 PM, Barry Smith wrote: >>>>> On Feb 26, 2016, at 9:28 AM, TAY wee-beng <[email protected]> wrote: >>>>> >>>>> Hi, >>>>> >>>>> I have got a 3D code. When I ran with 48 procs and 11 million cells, it >>>>> runs for 83 min. When I ran with 96 procs and 22 million cells, it ran >>>>> for 99 min. >>>> This is actually pretty good! >>> But if I'm not wrong, if I increase the no. of cells, the parallelism will >>> keep on decreasing. I hope it scales up to maybe 300 - 400 procs. > Hi, > > I think I may have mentioned this before, that is, I need to submit a > proposal to request for computing nodes. In the proposal, I'm supposed to run > some simulations to estimate the time it takes to run my code. Then an excel > file will use my input to estimate the efficiency when I run my code with > more cells. They use 2 mtds to estimate: > > 1. strong scaling, whereby I run 2 cases - 1st with n cells and x procs, then > with n cells and 2x procs. From there, they can estimate my expected > efficiency when I have y procs. The formula is attached in the pdf. > > 2. weak scaling, whereby I run 2 cases - 1st with n cells and x procs, then > with 2n cells and 2x procs. From there, they can estimate my expected > efficiency when I have y procs. The formula is attached in the pdf. > > So if I use 48 and 96 procs and get maybe 80% efficiency, by the time I hit > 800 procs, I get 32% efficiency for strong scaling. They expect at least 50% > efficiency for my code. To reach that, I need to achieve 89% efficiency when > I use 48 and 96 procs. > > So now my qn is how accurate is this type of calculation, especially wrt to > PETSc? > > Similarly, for weak scaling, is it accurate? > > Can I argue that this estimation is not suitable for PETSc or hypre? > > Thanks > > >>>>> So it's not that parallel. I want to find out which part of the code I >>>>> need to improve. Also if PETsc and hypre is working well in parallel. >>>>> What's the best way to do it? >>>> Run both with -log_summary and send the output for each case. This will >>>> show where the time is being spent and which parts are scaling less well. >>>> >>>> Barry >>> That's only for the PETSc part, right? So for other parts of the code, >>> including hypre part, I will not be able to find out. If so, what can I use >>> to check these parts? >> You will still be able to see what percentage of the time is spent in >> hypre and if it increases with the problem size and how much. So the >> information will still be useful. >> >> Barry >> >>>>> I thought of doing profiling but if the code is optimized, I wonder if it >>>>> still works well. >>>>> >>>>> -- >>>>> Thank you. >>>>> >>>>> Yours sincerely, >>>>> >>>>> TAY wee-beng >>>>> > > <temp.pdf>
