library

It the configure option "--enable-single-precision" is specified,
ELPA will also be build for single precision usage. The double precision
and single precision will be available at the same time with names
"solve_evp_real_1stage_double" or "solve_evp_real_1stage_single" and
so on...

This change immplied some major refactoring of the ELPA code:
1.) functions/procedures had to be renamed with suffix "_double"

2.) If necessary the same functions have to be available with suffix
"_single"

3.) Variable kind definitions have to be consistent with the
intented use

To avoid uneccessary code duplication this is done (most of the time)
with preprocessor string substitution.

The documentation has been updated.

NOT SUPPORTED are at the moment:

- single precision usage of ELPA2 with kernels, others than "generic"
  and "generic_simple"

- single precision usage of GPU

files

The test programs include the same template now, the
printed messages are thus unified

The configure flag "--enable-shared-memory-only" triggers a build
of ELPA without MPI support:

- all MPI calls are skipped (or overloaded)
- all calls to scalapack functions are replaced by the corresponding
  lapack calls
- all calls to blacs are skipped

Using ELPA without MPI gives the same results as using ELPA with 1 MPI
task!

This version is not yet optimized for performance, here and there some
unecessary copies are done.

Ths version is intended for users, who do not have MPI in their
application but still would like to use ELPA on one compute node

ELPA2 can now be build (as ELPA1) for single precision calculations.
The ELPA2 kernles which are implemented in assembler, C, or C++ have NOT
yet been ported.

Thus at the moment only the GENERIC and GENERIC_SIMPLE kernels support
single precision calculations

This version is not tested yet

ELPA2 can now be build (as ELPA1) for single precision calculations.
The ELPA2 kernles which are implemented in assembler, C, or C++ have NOT
yet been ported.

Thus at the moment only the GENERIC and GENERIC_SIMPLE kernels support
single precision calculations

With the configure option "--enable-single-precision" ELPA1 is build
with single-precision (half-words) only.

The best precision in single-precision (float or complex) is
2^-23 ~ 1.2e-7. The accuracy of the error residual of ELPA1 in
single-precision mode is of the order 1e-4 to 1e-5. The orthogonality of
the EV's is fullfilled up to about ~1e-6.

Thus the precision of ELPA1 in single-precision mode is roughly 100 -
1000 times less than the best achievable precison. This is consistent
with the double-precision mode, where also a factor of 100 - 1000 less
precision than the theoretical best one is found.

The float EVs are identical to the double EVs to at least 1e-2, the
precision of the EVs is thus about 1e-7/1e-2 = 1e5 times lower than the
best theoretical precision. If the same holds for the double precision
calculations, this implies that the double precision results can also
be only trusted on the level 1e-11 (5 orders of magnitude larger
than the best theoretical precision)

The best speed-up compared to the double precision calculation is
a factor of two. This is by far not achieved yet, since the singl
precision version is not at all optimized at the moment

As always the debug messages appear if the environment variable
is set

This commit is performance critical and has to be timed carefully.
Thus one can switch back to the old implementation. The new one,
however is more safe and better to debug

This commit might be performance critical, it has to be timed
carefully. Thus one can switch back to the old implementation.
The new one, however, is more safe and better to debug

This change might be performance critical and has to be timed
carefully. Thus it is possible to switch back to the old
implementation. The new one, however, can actually be debbuged