 Messages in this thread DateSun, 6 Jan 2002 11:16:59 -0800
(PST) From"M. Edward (Ed) Borasky" <> On Sun, 6 Jan 2002, wrote:
> Like dd if=/dev/zero of=/tmp/file bs=... count=... ? That
would do it, but I was trying to give a real-world example from
image processing, like copying a large image file.  > > #
perform a 2D in-place FFT of total size at least "MemTotal/2"
but less > > # than "MemTotal" > I'm willing to try. What
program can I use for FFT?  I use FFTW from  > Can you describe
FFT memory access pattern in more detail? > I'd like to write a
simple testcase with similar 'bad' pattern.  Imagine a 16384 by
16384 array of double complex values. That's a 4 GByte image.
Scale down to fit your machine, of course :). The first pass
will do an FFT on every row (column) if your language is C
(FORTRAN). The "stride" is 16 bytes (one complex value) in the
inner loop. Each row (column) is 16384*16 = 262144 bytes long,
which works out to 64 pages if the page size is 4096 bytes.
Then the second pass will do an FFT