[ET Trac] [Einstein Toolkit] #2158: Without MPI installed, Cactus doesn't build

[Einstein Toolkit]

#2158: Without MPI installed, Cactus doesn't build
-------------------------------+---------------------------------
  Reporter:  Steven R. Brandt  |      Owner:  (none)
      Type:  defect            |     Status:  review
  Priority:  unset             |  Milestone:
 Component:  Other             |    Version:  development version
Resolution:                    |   Keywords:
-------------------------------+---------------------------------

Comment (by Roland Haas):

 Looking at what HWLOIC is doing, it seems that it is setting HWLOC_DIR to
 "NO_BUILD" if it can find all the "-l" options from pkg-config but cannot
 extract a directory from the CFLAGS options that pkg-config reports. Which
 is not the same as if a variable was not set (by a user). It is an
 inability by hwloc to determine an installation prefix directory for
 itself. Admittedly given that Ubuntu now uses /usr/lib/x86_64-linux-gnu/
 instead of the traditional /usr/lib, a prefix (namely "/usr") is lees
 useful since one cannot expect anymore that given a prefix the include
 directory is prefix/include and the lib is prefix/lib (other than using
 the compatibility directories like /usr/lib/x86_64-linux-gnu/hdf5/serial/
 that are sometimes provided).

 I am not sure what the current agreed upon convention is? Can one expect
 that HWLOC_DIR/lib and HWLOC_DIR/include exist and contain the libs and
 header files or is all one can rely on that HWLOC_DIR is some directory
 associated with HWLOC (eg HWLOC_DIR/bin contains utilities)?

 Having HWCLOC_DIR set to NO_BUILD does indeed allow other
 externallibraries that require HWLOC take steps in case HWLOC is in a
 system location (which is why there is no -I in CFLAGS) and at least abort
 the build if the, for whatever reason, do need a prefix directory that is
 valid.

 Such a convention should ideally be documented in the minutes or wiki if
 possible to make sure that all thorns use the same magic value HWLOC uses
 NO_BUILD right now (so a different magic value). The same logic (and magic
 value) should then be implemented in all other ExternalLibraries.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/2158#comment:7>
Einstein Toolkit <http://einsteintoolkit.org>
The Einstein Toolkit