[petsc-dev] why does the Ubuntu PETSc package install coarray Fortran?

[Drew Parsons]

On 2020-06-01 10:48, Satish Balay wrote:
> This is likely a dependency of a dependency.
> 
> In rpm world - you can do something like:
> 
> [root at sb ~]# repoquery --whatrequires SuperLU.x86_64
> Last metadata expiration check: 0:07:55 ago on Sun 31 May 2020 09:38:39 
> PM CDT.
> SuperLU-devel-0:5.2.1-8.fc32.x86_64
> SuperLU-doc-0:5.2.1-8.fc32.x86_64
> armadillo-0:9.860.1-1.fc32.x86_64
> armadillo-0:9.880.1-1.fc32.x86_64
> freefem++-0:4.4.2-2.fc32.x86_64
> freefem++-0:4.6-1.fc32.x86_64
> hypre-0:2.18.1-2.fc32.x86_64
> mld2p4-serial-0:2.2.1-5.fc32.x86_64
> octave-iso2mesh-0:1.9.1-5.fc32.x86_64
> petsc-0:3.12.3-2.fc32.x86_64
> 
> I don't know what the equivalent in deb world is.
> 
> So I would manually check on some of the petsc dependencies
> 
> apt install libblas-dev
> 
> apt install libsuitesparse-dev
> 
> etc..
> 
> cc: Drew, perhaps has a better answer.
> 
> Satish
> 
> 
> 
> On Sun, 31 May 2020, Jeff Hammond wrote:
> 
>> I understand a lot of these but how does PETSc depend on OpenCoarrays?
>> 
>> Obviously, I do not fault the PETSc developers for this, because I 
>> know
>> they are not using coarray Fortran, but maybe somebody on this list 
>> knows
>> who is creating the Ubuntu packages for PETSc.
>> 
>> If there is a simple way to understand this using Apt, please share.  
>> I ran
>> apt-rdepend but do not see any reference to the coarrays stuff, so I 
>> don't
>> know how it is getting included here.
>> 
>> Jeff
>> 
>> $ sudo apt-get install petsc-dev
>> [sudo] password for jrhammon:
>> Reading package lists... Done
>> Building dependency tree
>> Reading state information... Done
>> The following additional packages will be installed:
>>   ksh libaec-dev libaec0 libamd2 libblas-dev libbtf1 *libcaf-openmpi-3
>> *libcamd2
>> libccolamd2 libcholmod3 *libcoarrays-openmpi-dev* libcolamd2

tl;dr: "apt-cache rdepends", "apt-rdepends -r"

Needed library dependencies get embedded in the shared libraries and can 
be read with objdump,
$objdump -p 
/usr/lib/petscdir/petsc3.12/x86_64-linux-gnu-real/lib/libpetsc_real.so.3.12.4

But you're asking at package level for the reverse dependencies of a 
package, which other packages depend on a given package. There are a 
couple of tools for that.

apt-cache from the apt package is short and simple, using the rdepends 
action

$ apt-cache rdepends libcoarrays-openmpi-dev libcamd2 libcaf-openmpi-3
libcoarrays-openmpi-dev
Reverse Depends:
   libopenmpi-dev
libcamd2
Reverse Depends:
   libsuitesparse-dev
   libcholmod3
libcaf-openmpi-3
Reverse Depends:
   libcoarrays-openmpi-dev

"apt-cache show <pkg>" prints the description for the package, including 
its Dependencies. Handy for double-checking that rdepends is giving you 
reverse-dependencies, not dependencies (it's easy to forget if you're 
looking forwards or backwards).

apt-rdepends (in the apt-rdepends package) gives the whole chain right 
to the end, possibly Too Much Information. Despite the name, 
"apt-rdepends libcamd2" actually gives forward dependencies (what 
libcamd2 depends on) (in apt-rdepends it's r for recursive, not 
reverse). To find the chain of reverse dependencies in the opposite 
direction, use "apt-rdepends -r libcamd2".

"apt-rdepend -b" generates the list of build-dependencies that the 
package needs to build it (sadly "apt-rdepends -b -r" does not work, so 
it's less straightforward to know which other packages use it as a 
Reverse-Dependency)

apt-rdepends and apt-cache might miss some references (e.g. Suggests 
rather than Depends).  This search from Rebecca Palmer can be useful for 
those cases
   pkg=libcamd2; grep-dctrl -w -F Pre-Depends,Depends,Recommends,Suggests 
-s Source "$pkg" 
/var/lib/apt/lists/*_debian_dists_unstable_main_binary-amd64_Packages ; 
grep-dctrl -w -s Package "$pkg" 
/var/lib/apt/lists/*_debian_dists_unstable_main_source_Sources

"apt-rdepends -r" libcamd2 tells us the chain is petsc - libcholmod3 - 
libcamd2
libcaf-openmpi-3 is needed by libcoarrays-openmpi-dev
libcoarrays-openmpi-dev is not a dependency for any package. It might be 
a build dependency for something, or possibly it's simply not used yet. 
Just an OpenMPI tool available for use.

In short, libcholmod3 from suitesparse uses libcamd2.