Reply-To: | | [log in to unmask][log in to unmask]> > Subject: Re: slow smoothing > > On Tue, 22 Apr 2008 16:42:46 +0100, Kathy Pearson <[log in to unmask]> wrote:= > > > >I have resolved the problem of slow smoothing locally at the command lin= > e=20 > by > >calling Linux to create a new subdirectory each time to receive the=20 > smoothed > >output files. Smoothing then takes .12 seconds per volume or about one > >minute in total for 460 input volumes. It takes an additional 10 second= > s > >for a Linux call to move the generated swaf* files into the same directo= > ry > >with the waf* files. > > > >Profiling the smoothing function reveals that much of its time is spent = > in > >the MATLAB exist function, so I'm not sure what a general solution acros= > s > >platforms might be for faster i/o. > > I'm not a high-level Linux guru, but I've played with Linux/Unix for some= > =20 > time now, and the idea that the speed depends on how many files are in th= > e=20 > directory sounds very strange to me, unless there's something weird going= > =20 > on with your hard disk. > > I often see things proceed more quickly at the beginning of a calculation= > ,=20 > and then a slow down (I haven't plotted it, but I assume it's reaching=20= > > some kind of steady-state rate asymptotically). I've always assumed it's= > =20 > a virtual memory thing. Something like pages getting sucked into RAM, bu= > t=20 > then in the steady-state pages have to be swept both in and out of RAM. > > Again, I don't know enough to say for sure that it shouldn't depend on th= > e=20 > number of files in the directory, but it sounds very strange to me. > > Cheers > > > > >Kathy Pearson > >UAB Psychology Dept. > >=3D=3D=3DA>>µ3 |