Re: distribution issues - moving zlib into HDF5...

> I agree with Ed's concern about the netCDF library not being able to read 
> netCDF files that are created using zlib.  Same goes for HDF5 
> itself.  However it's done, the libraries should have zlib available.

    If we want to make zlib a requirement, we should decide that for certain.
Then, if it's a requirement, we should make the absolute best attempt we can
to use the system's installed zlib - that's what it's there for.  Only if there
is no zlib installed on the system should we attempt to help the user install
a copy of zlib from the _zlib_ web-site.  We should _not_ be in the "business"
of distributing zlib.

> At first blush, Ed's solution seems to me like a good one.

    It's _very much_ against all the current open source "package" installation
systems' philosophy and I don't think it's a good idea.  All of package
installation systems allow each package in the system to list other packages as
prerequisites that must be installed on the system before the package the
user is interested in is installed.  We just _finished_ removing zlib and
libjpeg from the HDF4 distribution... :-)

    Shipping someone else's library with our package and installing it
on a user's system (most likely _in place of_ the system version of that
library) has caused _lots_ of headaches for us in the past.

    Frankly, I think this is the course that netCDF-4 should take with HDF5
also, but that'll ultimately be up to them.

    Quincey

> Mike
> 
> At 03:17 PM 3/14/2006, Elena Pourmal wrote:
> >Ed,
> >
> >By default HDF5 tries to find zlib on the system and include it. Most of 
> >the systems will have zlib library installed.
> >
> >Including zlib with the source code may do more harm than good because 
> >users may end up with multiple versions of the zlib library.
> >
> >Let's see what other people will say.
> >
> >Elena
> >
> >At 02:37 PM 3/14/2006, Ed Hartnett wrote:
> >>Elena Pourmal <epourmal@xxxxxxxxxxxxx> writes:
> >>
> >> > Hi Ed,
> >> >
> >> > Zlib is optional for HDF5. We intentionally didn't put zlib with HDF5
> >> > source as we did many years ago for HDF4.
> >>
> >>Yes, I can see that.
> >>
> >> >
> >> > Are you talking about source code or binary distribution?
> >>
> >>Source code.
> >>
> >> >
> >> > Would it be possible for you to make zlib optional for NetCDF-4? Could
> >> > you explain more about shared libraries problem?
> >>
> >>Would it be possible? Yes.
> >>
> >>Would it be desirable? I don't think so.
> >>
> >>The problem with making it optional is that then someone can easily
> >>produce a netCDF-4 file that won't be readable is some places because
> >>zlib is not built into netcdf-4 somewhere.
> >>
> >>(That is, a user with zlib-enabled netCDF-4 can create the file, and
> >>send it to someone without zlib in netCDF-4, who would then be unable
> >>to read it. And would then send me a support email for me to
> >>handle. In which I will tell him to build netCDF-4 with zlib. So why
> >>not save all that trouble, and *always* build netCDF-4 with zlib?)
> >>
> >>What is the benefit if *not* having zlib installed? It is tiny and
> >>easy to include. Leaving it out gains nothing that I can see.
> >>
> >>Right now, netCDF-4 *requires* that HDF5 be built with zlib. I am
> >>trying to get a configuration tarball together to support that.
> >>
> >>Unless someone can present a very good reason for doing so, I don't
> >>see why there should be two versions of netCDF-4 out there, one with,
> >>and one without zlib.
> >>
> >>So the question becomes: how to get one tarball to work for netCDF-4,
> >>including zlib. The easiest way would be in HDF5 included zlib, and I
> >>may have to hack the HDF5 configuration to do this in the case of the
> >>netCDF-4 master tarball.
> >>
> >>But it would be so much easier if this was done at HDF5 HQ, instead of
> >>my me in my garage...
> >>
> >>Ed
> >>--
> >>Ed Hartnett  -- ed@xxxxxxxxxxxxxxxx
> >
> >-----------------------------------------------------------------------------------------------
> >Elena Pourmal, HDF QA, Maintenance and Support Team Leader
> >NCSA University of Illinois at Urbana-Champaign
> >605 E. Springfield Ave.
> >Champaign, IL 61820
> >
> >epourmal@xxxxxxxxxxxxx
> >(217)333-0238 (office)
> >(217)244-1987 (fax)
> >----------------------------------------------------------------------------------------------
> 
> --
> Mike Folk, Scientific Data Tech (HDF)   http://hdf.ncsa.uiuc.edu
> NCSA/U of Illinois at Urbana-Champaign  Voice: 217-244-0647
> 1205 W. Clark St, Urbana IL 61801    Fax: 217-244-5521  
>