[petsc-dev] user makefile

[Jed Brown]

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):
>> >>
>> >>
>> >>
>> >>
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>> >>
>> >>
>> >> *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/>
>>