[daip] VTESS problems under g77 3.2.2

[rlaing at eso.org]

On Mon, 29 Nov 2004, Eric Greisen wrote:

> rlaing at eso.org writes:
> 
>  > I recently attempted to use VTESS under a version of 31DEC04 downloaded and
>  > compiled on 2004 Jan 16 using g77/gcc 3.2.2 under Linux RH9. This failed
>  > consistently on a number of datasets, giving 0 and NaN for step and gradient,
>  > and always generating a flat image. Reverting to a VTESS.EXE compiled using
>  > an older g77 under RH6.3 gave sensible results [I'll send fuller details if they
>  > are of any use to you].
>  > 
>  > Would you recommend returning to gcc 2.95.3 or is there a known work-around for
>  > 3.2.2 (e.g. in a more recent incarnation of 31DEC04)?
> 
> I just rebuild my system with the RH9 build 3.2.2 compiler and ran a
> VTESS with which I am familiar and it produced answers identical to
> those of 3.2.3 and certainly not NaN's and such.
> 
> 2.95.3 is always a solution so far but perhaps this needs more
> debugging.
> 
> VTESS is a very touchy program and can go off into the weeds pretty
> easily but usually not with NaN's.  Are you using a positive value of
> FLUX - try a negative value.  Does it produce the Nan's immediately or
> only after some iterations?  perhaps I need to see the inputs and
> maybe even use one of your images...
> 

Dear Eric

I've tried various combinations of inputs (flux positive, negative and zero) and
several input datasets, albeit similar to each other. The problem occurs
consistently on the first iteration and every iteration thereafter. I ran the
old executable immediately afterwards with the same inputs from a private
version and got sensible results. I will put together a tarball of inputs,
datasets and results with the new and old versions for you shortly.

Thanks

Robert

-- 
Robert Laing
European ALMA Instrument Scientist

European Southern Observatory
Karl-Schwarzschild-Strasse 2
D-85748 Garching-bei-Muenchen
Germany

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rlaing at eso.org