Alternative SLEPc builds for slepc4py
=====================================

slepc4py is available for python3 with support for 
real numbers (python3-slepc4py-real)
and complex numbers (python3-slepc4py-complex).

Either build is accessible at runtime.  By default slepc4py uses the
default SLEPc build set in /usr/lib/slepc (which can be selected with
"update-alternatives --config slepc")

Other SLEPc builds can be selected at runtime by setting (or exporting)
the SLEPC_DIR environment variable.

Examples include:

SLEPC_DIR=/usr/lib/slepcdir/slepc-real
 selects the preferred real-number version of SLEPc, by default the
 latest version, but can be selected with
 "update-alternatives --config libslepc_real.so"

SLEPC_DIR=/usr/lib/slepcdir/slepc-complex
 selects the preferred complex-number version of SLEPc, by default the
 latest version, but can be selected with
 "update-alternatives --config libslepc_complex.so"


Specific SLEPc versions and builds as found under /usr/lib/slepcdir
(or elsewhere) can also be selected with SLEPC_DIR.


For example,
  SLEPC_DIR=/usr/lib/slepcdir/slepc-complex python3 -c "import slepc4py; print(slepc4py.__path__)"
prints the path to the slepc4py module built against the preferred
complex-number build of SLEPc.


The PETSC_DIR environment variable corresponding to the given
SLEPC_DIR should also be set, of course.
