thanks Akio hopefully you will contribute the code back if/when you get it working? Bruce
On Wed, 4 Jul 2012, Akio Yamamoto wrote: > Hi Bruce and Richard, > > Yes, as Richard pointed out, I just wanted to know the numbers for input > to Amdahl's law, if you have already something, to figure out the maximum > expected speedup using multiple processors/cores. > > As for improvements of em_reg, I'll try to split each transform as well as > parallelize the energy evaluation. > > Thank you for your comments. > > Akio > > (2012/07/04 5:21), R Edgar wrote: >> On Tue, Jul 3, 2012 at 3:48 PM, Bruce Fischl <fis...@nmr.mgh.harvard.edu> >> wrote: >> >>> I think that the theoretical ratio is much bigger than what you would be >>> able to achieve in practice. It's hard to compute exactly, but for example >>> for em_reg it should be the number of samples (which are processed >>> independently), so something on the order of 1000. For ca_reg it should be >>> bigger, but it's a bit more complicated as things aren't independent. >> I _hope_ that the OpenMP version of mri_em_reg doesn't just try >> parallelising the energy evaluation - it would be better to split each >> transform off as a separate work item for handling by the available >> threads (similar to what I did on the extra-fast GPU version). This >> keeps the individual pieces of work big, which is good for CPUs >> >> I think that what Akio's after are the numbers to plug into Amdahl's >> Law. I don't think that these are easy to work out for anything in >> Freesurfer. But you can put timers around the parallel sections, and >> see what speed up you get on those. >> >> HTH, >> >> Richard >> _______________________________________________ >> Freesurfer mailing list >> Freesurfer@nmr.mgh.harvard.edu >> https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer >> >> >> The information in this e-mail is intended only for the person to whom it >> is >> addressed. If you believe this e-mail was sent to you in error and the >> e-mail >> contains patient information, please contact the Partners Compliance >> HelpLine at >> http://www.partners.org/complianceline . If the e-mail was sent to you in >> error >> but does not contain patient information, please contact the sender and >> properly >> dispose of the e-mail. >> >> >> > > > > _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
