Re: [alma-sw-ssr] Offline Requirements v3.1

[Mark Holdaway <mholdawa@nrao.edu>]

> > 
> > The current req text reflects what I thought we had decided (though the
> > parenthetical Comment may not) - it is allowed, for nominal cost.  I would
> > say an IDL liscense as it stands is more than "nominal".  My experience
> > (with MATLAB and IDL) is that you take a tremendous performance hit
> > using these packages, one I doubt we can afford given the processing
> > requirements.  
> 
> i can confirm this.  i did detailed tests of this a few years ago when
> simulating holography errors - i.e., lots of FFT/DFTs.  the difference
> between optimized FORTRAN and IDL implementations was about a factor of
> 20 in speed.  you can see more details at:
> http://www.aoc.nrao.edu/~bbutler/work/nraomemos/holo_sim.ps.gz
> if you want (see table 1).
> 
> while packages like IDL and matlab are very nice when visualizing things,
> and for smaller problems, they just cannot deliver the speed we will need
> (in my experience/opinion) for ALMA data processing.
> 

I see some important uses of an IDL-like package: 

  * prototyping imaging or calibration algorithms -- trying
    things out before you hard code them
  * display - visualization - problem-solving: if you don't
    know what is wrong with your data, IDL or something similar
    may be useful in exploring and understanding the data
  * post imaging analysis: the imaging will be the big time
    consuming step.  After you make the image, you want to
    be able to perform some sort of quantitative analysis on
    the image -- and this analysis may be non-standard and
    experimental.

AIPS++'s glish seeks to do these jobs already, and will probably succeed
to a large degree.  Glish is powerful in that it will already be
well-integrated with the data and other aspects of the data processing
(ie, efficiently coded tasks written with C++ and Fortran code), but is
not nearly as familiar to so many people nor as polished as something like
IDL.

So, I think much of the functionality you would get from IDL is there
in glish, so it comes down to a political choice: make people learn a
new package, or give them what some of them know already?

	-Mark