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How to install ELPA
===================
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First of all, if you do not want to build ELPA yourself, and you run Linux,
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it is worth having a look at the ELPA webpage http://elpa.rzg.mpg.de
and/or the repositories of your Linux distribution: there exist
pre-build packages for a number of Linux distributions like Fedora,
Debian, and OpenSuse. More, will hopefully follow in the future.
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If you want to build (or have to since no packages are available) ELPA yourself,
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please note that ELPA is shipped with a typical "configure" and "make"
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autotools procedure. This is the only supported way how to build and install ELPA.
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If you obtained ELPA from the official git repository, you will not find
the needed configure script! Please look at the "INSTALL_FROM_GIT_VERSION" file
for the documentation how to proceed.


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If --- against our recommendations --- you do not want to install ELPA as
library, but to include it in your source code you will have to find a solution
by yourself. If you do this anyway, please distribute then all files of ELPA
with your code.
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(A): Installing ELPA as library with configure
===================================================

The configure installation is best done in four steps

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1) run configure:

   Check the available options with "configure --help".
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   ELPA is shipped with several different versions of the
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   elpa2-kernel, each is optimized and tuned for a different
   architecture.

1.1) Choice of ELPA2 kernels

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   With the release of ELPA (2014.06 or newer) it is _not_
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   mandatory any more to define the (real and complex) kernels
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   at build time. The configure procedure will build all the
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   kernels which can be used on the build system. The choice of
   the kernels is now a run-time option. This is the most
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   convenient and also recommended way. It is intended to augment
   this with an auto-tuning feature.

   Nevertheless, one can still define at build-time _one_
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   specific kernel (for the real and the complex case each).
   Then, ELPA is configured only with this real (and complex)
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   kernel, and all run-time checking is disabled. Have a look
   at the "configure --help" messages and please refer to the
   file "./src/elpa2_kernels/README_elpa2_kernels.txt".


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1.2 Setting up Blacs/Scalapack
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   The configure script tries to auto-detect an installed Blacs/Scalapack
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   library. If this is successful, you do not have to specify anything
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   in this regard. However, this will fail, if you do not use Netlib
   Blacs/Scalapack but vendor specific implementations (e.g. Intel's MKL
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   library or the implementation of Cray and so forth...).
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   In this case, please  point to your Blacs/Scalapack installation and the
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   link-line with the variables "SCALAPACK_LDFLAGS" and "SCALAPACK_FCFLAGS".
   "SCALAPACK_LDFLAGS" should  contain the correct link-line for your
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   Blacs/Scalapack installation and "SCALAPACK_FCFLAGS" the include path
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   and any other flags you need at compile time.

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   For example with Intel's MKL 11.2 library one might have to set

   SCALAPACK_LDFLAGS="-L$MKLROOT/lib/intel64 -lmkl_scalapack_lp64 -lmkl_intel_lp64 \
                      -lmkl_sequential -lmkl_core -lmkl_blacs_intelmpi_lp64 \
		      -lpthread -lm -Wl,-rpath,$MKL_HOME/lib/intel64"
   and

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   SCALAPACK_FCFLAGS="-I$MKLROOT/include/intel64/lp64"
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   Note, that the actual MKL linkline depends on the installed MKL version.

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   If your libraries are in non-standard locations, you can think about
   specifying a runtime library search path ("rpath") in the link-line,
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   otherwise it will be necessary to update the LD_LIBRARY_PATH environment
   variable.

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   In any case, auto-detection or manual specification of Blacs/Scalapack,
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   the configure procedure will check whether Blacs/Scalapack is available
   at build-time and try to link with it.
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1.3 Setting optimizations
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   Please set the optimisation that you prefer with the
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   variable "FCFLAGS", "CFLAGS", and "CXXFLAGS",
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   please see "./src/elpa2_kernels/README_elpa2_kernels.txt".

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   Note that _NO_ compiler optimization flags are set automatically. It
   is always adviced to set them by e.g.:
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   ./configure CFLAGS="-O2" CXXFLAGS="-O2" FCFLAGS="-O2"
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   Note that it is mandatory to set optimization flags for C, C++, and Fortran
   since ELPA uses source files and compile steps from all these languages.

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   Also note that building of the SSE and AVX kernels, requires
   compilation with the GNU C Compiler (gcc). It is advised to
   set also CFLAGS="-march=native" CXXFLAGS="-march=native",
   since otherwise the GNU compiler does not support AVX, even
   if the hardware does. If you already included "-mAVX" in the
   flags, you can skip "-march=native".

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   If you want to use the newer AVX2 instructions, assuming they are supported on
   your hardware, please set CFLAGS="-march=avx2 -mfma" and CXXFLAGS="-march=avx2 -mfma".

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   Setting the optimization flags for the AVX kernels can be a hassle. If AVX
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   kernels are build for your system, you can set the configure option
   "--with-avx-optimizations=yes". This will automatically set a few compiler
   optimization flags which turned out to be beneficial for AVX support.
   However, it might be that on your system/compiler version etc. other flags
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   are the better choice. AND this does _not_ set the above mentioned flags,
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   which you should still set by hand:

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   ./configure CFLAGS="-O2" CXXFLAGS="-O2" FCFLAGS="-O2"
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   An istallation with AVX2 and best-optimizations could thus look like this:

   ./configure  CFLAGS="-O2 -mavx2 -mfma" CXXFLAGS="-O2 -mavx2 -mfma" FCFLAGS="-O2" --with-avx-optimization
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1.4 Installation location

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   Set the "--prefix" flag if you wish another installation location than
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   the default "/usr/local/".

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1.5 Hybrid OpenMP support

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   If you want to use the hybrid MPI/OpenMP version of ELPA please specify
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   "--enable-openmp". Note that the ELPA library will then contain a "_mt" in
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   it's name to indicate multi threading support.
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1.6 Other
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   Note, that at the moment we do not officially support "cross compilation"
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   although it should work.
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2) run "make"

3) run "make check"
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   A simple test of ELPA is done. At the moment the usage of "mpiexec"
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   is required. If this is not possible at your system, you can run the
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   binaries

     elpa1_test_real
     elpa2_test_real
     elpa1_test_complex
     elpa2_test_complex
     elpa2_test_complex_default_kernel
     elpa2_test_complex_choose_kernel_with_api
     elpa2_test_real_default_kernel
     elpa2_test_real_choose_kernel_with_api

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   yourself. At the moment the tests check whether the residual and the
   orthogonality of the found eigenvectors are lower than a threshold of
   5e-12. If this test fails, or if you believe the threshold should be
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   even lower, please talk to us. Furthermore, your run-time choice of
   ELPA kernels is tested. This is intended as a help to get used to this
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   new feature. With the same thought in mind, a binary "elpa2_print_kernels"
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   is provided, which is rather self-explanatory.
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   Also some of the above mentioned tests are provided as C source files.
   These should demonstrate, how to call ELPA from a C program (i.e. which headers to include
   and call the ELPA functions). They are NOT intended as a copy and paste solution!

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4) run "make install"
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   Note that a pkg-config file for ELPA is produced. You should then be
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   able to link the ELPA library to your own applications.


B) Installing ELPA without the autotools procedure
===================================================
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   We do not support installation without the autotools anymore!
   If you think you need this, sorry, but then you are on your own.


How to use ELPA
===============

Using ELPA should be quite simple. It is similar to ScalaPack but the API
is different. See the examples in the directory "./test". There it is shown how
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to evoke ELPA from a Fortran code.

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If you installed ELPA, a pkg-config file is produced which will tell you how to
link your own program with ELPA.