[Insight-users] PCAShapeModelEstimator -- seems way too slow?

[Lydia Ng]

Zach,

Out of curiosity - could you post info about the compiler and compile =
flags
that you used on your G4?

- Lydia

> -----Original Message-----
> From: Zachary Pincus [mailto:zpincus@stanford.edu]
> Sent: Friday, May 14, 2004 12:20 AM
> To: ITK
> Subject: [Insight-users] PCAShapeModelEstimator -- seems way too slow?
>=20
> Hello,
>=20
> Recently, I've been doing some PCA work, and I noticed that itk's
> ImagePCAShapeModelEstimator seems to be surprisingly slow.
>=20
> I have, for example, 1100 images of size 20x15 -- a pretty modest data
> set to do PCA on. Matlab (running on a 450 MHz ultrasparc-II) can
> compute the principal components on such a dataset in a few seconds,
> even when I intentionally do things in a particularly slow way.
>=20
> Using the ITK PCA estimator, this same operation takes 15+ minutes on
> my personal machine (867 mhz g4). It's not a RAM or VM issue since the
> process never seems to grab more than 100 megs of RAM, and doesn't hit
> the disk at all.
>=20
> This seems especially strange given the effort in the PCA class's
> implementation toward efficiency. (Though I do realize that a dataset
> such as mine with more images than pixels per image does defeat some =
of
> the optimizations rolled in...)
>=20
> What could I possibly be doing wrong? I profiled the itk PCA code, and
> nothing looks overtly wrong -- it just seems to take way too long!
>=20
> Zach Pincus
>=20
> Department of Biochemistry and Program in Biomedical Informatics
> Stanford University School of Medicine
>=20
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