"Smith, Barry F. via petsc-dev" <petsc-dev@mcs.anl.gov> writes:
>> On Jun 26, 2019, at 9:56 AM, Balay, Satish via petsc-dev >> <petsc-dev@mcs.anl.gov> wrote: >> >> On Wed, 26 Jun 2019, Jakub Kruzik via petsc-dev wrote: >> >>> Hello, >>> >>> as I mentioned in PR #1819, I would like to use SLEPc in PETSc. >>> >>> Currently when PETSc is configured with --download-slepc, it defines >>> PETSC_HAVE_SLEPC and each compilation of PETSc recompiles SLEPc. >> >> yes - slepc uses petsc, so when petsc is updated - its best to rebuild slepc >> >> You can ignore PETSC_HAVE_SLEPC flag [its just a build tool thingy] >> PETSc code does not use this flag - and there is no circular >> dependency. >> >>> The first way to use SLEPc is from an example. That should be easy, all we >>> need is to add -lslepc when compiling an example. >> >> Its best to use slepc examples as templates - and slepc makefiles [as >> examples]. >> >> --download-slepc is a convinence feature to install petsc and slepc in >> a single go. It does not change how you would use slepc. >> >> Satish >> >> >>> >>> The other option is to use SLEPc inside PETSc code. I do not know how to >>> achieve this. One way could be to define PETSC_HAVE_SLEPC after the >>> compilation of SLEPc and again compile PETSc but this time linking with >>> SLEPc. >>> Although, even if it works, it is ugly. > > If you make SLEPc calls from PETSc source you should only need the SLEPc > header files to compile the PETSc source; not the SLEPc library. So one way > to accomplish this would be to do a "partial" install of SLEPc, build PETSc > (that uses SLEPc) and then complete the SLEPc install. When --download-slepc > is used this would mean during the SLEPc.py script it would copy over the > SLEPc include files to the prefix location and after PETSc is built it would > build the SLEPc libraries and move them to the prefix location. The on iffy > thing is that SLEPc include files may depend on generated PETSc include files > (which are not fully generated until configure is done). Thus instead of > having SLEPc.py move the SLEPc include to the prefix location it would need > to post-pone that until just at the end of configure (we have other packages > to do this). So when you ready to try this out let us know and we can help > with the infrastructure. (it will avoid 2 builds of either PETSc or SLEPc). That is disgusting. If code in libpetsc.so depends on libslepc.so, then you'd have a circular dependency. You can implement and register a PC in SLEPc (it would go in libslepc.so).
