[daip] Problem with 31DEC05 IMAGR with CMETHOD ''

[Eric Greisen]

Subhashis Roy writes:

 > It appears that with CMETHOD '', the present algorithm (07DEC05) is not correct to
 > choose the fastest method when IMSIZE=128i. It is not selecting GRID at
 > all in this case (It appears to be fine when IMSIZE=256).  
 > (this run is on i386 compiled with gcc-2.95.3).
 > 
 > This is making it extremely slow (last step of removing ~10000 comp took
 > 15 minutes) on my amd64 2.2GHz machine (~3.2 GHz P-IV). Clearly, FFT is
 > much faster here.
 > 

Yes - there is an issue here not only of speed but of accuracy.  We
discovered that our source models did not work correctly when we
provided a small subimage together with the CC file.  The default
method was always gridded and the results were bad because it made a
small grid and then tried to interpolate over very large u-v cells.

We now force DFT when the image is not a power of 2 or when the images
average <= 128.  That is pretty arbitrary and could be set < 128.

I should try things for a while before I am willing to change this
however.  We did find another problem with the models which might have
been the real cause of the earlier trouble.  As I say, I will have to
experiment.

You could experiment too - the subroutine is $APLSUB/FORCED.FOR.  Edit
it, then
COMRPL $APLSUB/FORCED
COMLNK $APGOOP/IMAGR

Eric Greisen