I see; well that's a fair point. So i have my timing results obtained via -log_summary; what should I be looking into for MatMult? Should I be looking at wall timings? Or do I need to look into MFlops/s? I'm sorry but I'm not sure what measure I should be looking into to determine scalability.
Also, is there any general meaningful advice one could give? in terms of using the resources, compiler flags (beyond -O3), etc? Thanks, Mohammad On Fri, May 18, 2012 at 4:18 PM, Matthew Knepley <knepley at gmail.com> wrote: > On Fri, May 18, 2012 at 7:06 PM, Mohammad Mirzadeh <mirzadeh at > gmail.com>wrote: > >> Hi guys, >> >> I'm trying to generate scalability plots for my code and do profiling and >> fine tuning. In doing so I have noticed that some of the factors affecting >> my results are sort of subtle. For example, I figured, the other day, that >> using all of the cores on a single node is somewhat (50-60%) slower when >> compared to using only half of the cores which I suspect is due to memory >> bandwidth and/or other hardware-related issues. >> >> So I thought to ask and see if there is any example in petsc that has >> been tested for scalability and has been documented? Basically I want to >> use this test example as a benchmark to compare my results with. My own >> test code is currently a linear Poisson solver on an adaptive quadtree grid >> and involves non-trivial geometry (well basically a circle for the boundary >> but still not a simple box). >> > > Unfortunately, I do not even know what that means. We can't guarantee a > certain level of performance because it not > only depends on the hardware, but how you use it (as evident in your > case). In a perfect world, we would have an abstract > model of the computation (available for MatMult) and your machine (not > available anywhere) and we would automatically > work out the consequences and tell you what to expect. Instead today, we > tell you to look at a few key indicators like the > MatMult event, to see what is going on. When MatMult stops scaling, you > have run out of bandwidth. > > Matt > > >> Thanks, >> Mohammad >> > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120518/b1697b93/attachment.htm>
