I'm wondering if anyone has modified the SPM99 code in order to deal with
large fixed-effects regressions. Right now I'm doing a fixed effects
analysis of 118 (!) sessions for fMRI, and it's quite slow. (I realize that
the code as originally written wasn't really intended for that kind of work;
that the community is moving to random effects analyses; etc.) (The
bottlenecks to doing many sessions efficiently are a few SVDs and matrix
multiplications, where the different sessions are "separable" but the code
doesn't take advantage of that.)
The other issue is reslicing, since that's the most typical (pre)processing
bottleneck. The SPM code itself looks good, but it appears to call some
matlab routines. While these might be quite efficient algorithmically, I
thought perhaps they could be speeded up by recoding them in C and then
creating a mex file.
Best,
Steve Fromm
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