Should BuildSystem download updated external packages when they are out of date?

[Barry Smith]

On Oct 2, 2009, at 9:38 AM, Matthew Knepley wrote:

> On Fri, Oct 2, 2009 at 9:11 AM, Richard Tran Mills <rmills at climate.ornl.gov 
> > wrote:
> BuildSystem Folks (Matt, mainly),
>
> This is not really a problem for me since I know about this behavior  
> already, but I note that it can cause significant confusion when  
> configure.py has been asked to download a package and a very out of  
> date version of that package already exists in $PETSC_DIR/ 
> externalpackages.  In this case, configure.py doesn't do anything  
> since the package is already there, but in some cases the interfaces  
> have changed and that package isn't actually usable.  For instance,  
> if hypre-2.0.0 is present, it won't work with the current petsc-dev,  
> but the configure proceeds anyway, even though things won't work  
> unless hypre-2.4.0b is downloaded.  In such a case, deleting the  
> hypre-2.0.0 directory and re-running configure.py will fix the  
> problem, but it seems like this isn't very user-friendly and I know  
> that it does cause some confusion.
>
> I am no BuildSystem hacker (I think I've committed a change maybed  
> once, in 2005?).  Can someone tell me if it is reasonable to make  
> configure.py download the new package if the old one is too out of  
> date?
>
> This is the versioning problem, which has no good resolution. The  
> way I understand things, with a given version of PETSc, this problem
> cannot arise, UNLESS it is petsc-dev. I am willing to live with this  
> problem in petsc-dev, rather than introduce some versioning scheme
> which is just as broken as the current scheme.

    Yes it should only happen in petsc-dev.

    See my proposed "solution"; it is just a few lines of code and  
will eliminate most problems I believe without introducing a  
complicated overhead. What do you think?
Even if someone changes the tarball's name this will also cause and  
extra download which is harmless enough.
    Barry

>
>    Matt
>
> Sincerely,
> Richard
> -- 
> What most experimenters take for granted before they begin their  
> experiments is infinitely more interesting than any results to which  
> their experiments lead.
> -- Norbert Wiener