[petsc-dev] user makefile

[Barry Smith]

  I'll take a stab at fixing up the description of possible makefile approaches in the user's manual documentation and put it in an MR. I agree with Mark it is weak.

  Barry


> On Jan 14, 2022, at 10:41 AM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Makefile.user is meant to be the example that doesn't import a zillion variables and in which you can readily add other packages that provide pkg-config. (Just add them to one line.) If you already use pkg-config for other dependencies, it also makes clear how to add PETSc. This is symmetric, where as including PETSc makefiles is fundamentally nonsymmetric (they're full of rules and non-namespaced variables likely to conflict with other packages).
> 
> While we could create a makefile that defines only namespaced variables and does not define rules, that would actually require more effort per package because you'd be needing CPPFLAGS = $(PETSC_CPPFLAGS) $(X_CPPFLAGS) $(Y_CPPFLAGS). In Makefile.user, you can add additional packages with one line.
> 
> PACKAGES := $(petsc.pc) $(x.pc) $(y.pc)
> 
> where the x.pc variable can either be the plain package name (to look for it in default locations) or a path to the x.pc file.
> 
> Mark Adams <mfadams at lbl.gov> writes:
> 
>> I want an example that I can clone for an existing makefile. I don't even
>> see PETSC_LIB in Makefile.user
>> 
>> Makefile.user is where you start if 0) you are starting from scratch and
>> are all-in on PETSc.
>> 
>> I think the vast majority of our users either 1) have a makefile and want
>> to add PETSc or 2) want to keep more control than this turn-key method.
>> 
>> I think something like Victor's material is useful even if it goes out of
>> date (
>> https://pages.tacc.utexas.edu/~eijkhout/taccnotes/petsclinking/petsclinking.html
>> ).
>> 
>> Barry's "Writing Application Codes with PETSc" addresses (0) and then jumps
>> to 3) no makefile just cut and paste (nice, not what I'm looking for, but
>> cleaner than making an example).
>> 
>> (I have literally never done any of the methods, shown in the PETSc docs,
>> before. I have alway owned the makefile with my targets, and all of my
>> current users do this now.)
>> 
>> The first thing I googled was "petsc user makefile" and found and
>> interesting stackoverflow post (
>> https://stackoverflow.com/questions/21338718/using-petsc-on-makefile-within-my-user-defined-makefile
>> )
>> 
>> Maybe just a FAQ "Adding PETSc to a user Makefile" and you could just have
>> a link to Victor's page (and have him update the include path line)
>> 
>> 
>> On Thu, Jan 13, 2022 at 11:15 PM Jed Brown <jed at jedbrown.org> wrote:
>> 
>>> No makefile is needed to build foo from foo.c.
>>> 
>>> $ make -f $PETSC_DIR/share/petsc/Makefile.user foo
>>> 
>>> 
>>> In the example below, you don't have to write the recipe (the ${CLINKER}
>>> line). It's enough to write
>>> 
>>> foo: foo.o baz.o
>>> 
>>> Matthew Knepley <knepley at gmail.com> writes:
>>> 
>>>> foo: foo .o
>>>>      ${CLINKER} -o $@ $^ ${PETSC_LIB}
>>>> 
>>>>   Matt
>>>> 
>>>> On Thu, Jan 13, 2022 at 9:54 PM Jacob Faibussowitsch <
>>> jacob.fai at gmail.com>
>>>> wrote:
>>>> 
>>>>> Is share/petsc/Makefile.user what you are looking for?
>>>>> 
>>>>> Best regards,
>>>>> 
>>>>> Jacob Faibussowitsch
>>>>> (Jacob Fai - booss - oh - vitch)
>>>>> 
>>>>> On Jan 13, 2022, at 21:49, Barry Smith <bsmith at petsc.dev> wrote:
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>> https://petsc.org/release/docs/manual/getting_started/?highlight=user%20makefile
>>>>> 
>>>>> Search for Writing Application Codes with PETSc
>>>>> 
>>>>> Perhaps this needs to clearer or have links to it from the FAQ.
>>>>> 
>>>>> 
>>>>> 
>>>>> On Jan 13, 2022, at 9:38 PM, Mark Adams <mfadams at lbl.gov> wrote:
>>>>> 
>>>>> I am finding it pretty hard to find an example of a makefile target to
>>>>> build an app with PETSc.
>>>>> 
>>>>> I can not find it on the docs page.
>>>>> 
>>>>> With Google:
>>>>> 
>>>>> Victor has a little example that looks fine ($PETSC_LIB). (sort of, see
>>>>> below)
>>>>> 
>>>>> Another one is bigger and has this at the end:
>>>>> 
>>>>>    -${CLINKER} $< -o bin.x $(OBJ_FILES) ${PETSC_KSP_LIB}
>>>>> -I$(PETSC_DIR)/include
>>>>> 
>>>>> I recall using PETSC_KSP_LIB the last time I wrote a makefile 20 years
>>> ago.
>>>>> 
>>>>> Maybe there should be a FAQ that a search would find like "Example of
>>> user
>>>>> makefile" with something like Victor's (dropping v2 and updating it,
>>> this
>>>>> looks wrong):
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> *PETSc linkingThe easiest way to link PETSc to your code is to have this
>>>>> line in your makefile:include ${PETSC_DIR}/conf/baseThis will
>>> automatically
>>>>> give you the compilation rules. For linking you then do:${CLINKER} -o
>>> ex1
>>>>> ex1.o ${PETSC_LIB}(or FLINKER for fortran)You can also use this include
>>>>> line:include ${PETSC_DIR}/conf/variablesand then you have to give the
>>>>> compile rules yourself. In this case, dosomething like${CC} -c ex1.c
>>>>> ${PETSC_INCLUDE}to compile. (This is for petsc version 3, for version 2
>>>>> useinclude ${PETSC_DIR}/bmake/common/baseand replace base by variables
>>> to
>>>>> omit petsc’s make rules.)If you insist on having all the libraries and
>>>>> includes explicitly, usemake getlinklibsmake getincludedirs*
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> --
>>>> 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
>>>> 
>>>> https://www.cse.buffalo.edu/~knepley/ <
>>> http://www.cse.buffalo.edu/~knepley/>
>>>