!    This file is part of ELPA.
!
!    The ELPA library was originally created by the ELPA consortium,
!    consisting of the following organizations:
!
!    - Max Planck Computing and Data Facility (MPCDF), formerly known as
!      Rechenzentrum Garching der Max-Planck-Gesellschaft (RZG),
!    - Bergische Universität Wuppertal, Lehrstuhl für angewandte
!      Informatik,
!    - Technische Universität München, Lehrstuhl für Informatik mit
!      Schwerpunkt Wissenschaftliches Rechnen ,
!    - Fritz-Haber-Institut, Berlin, Abt. Theorie,
!    - Max-Plack-Institut für Mathematik in den Naturwissenschaften,
!      Leipzig, Abt. Komplexe Strukutren in Biologie und Kognition,
!      and
!    - IBM Deutschland GmbH
!
!
!    More information can be found here:
!    http://elpa.mpcdf.mpg.de/
!
!    ELPA is free software: you can redistribute it and/or modify
!    it under the terms of the version 3 of the license of the
!    GNU Lesser General Public License as published by the Free
!    Software Foundation.
!
!    ELPA is distributed in the hope that it will be useful,
!    but WITHOUT ANY WARRANTY; without even the implied warranty of
!    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!    GNU Lesser General Public License for more details.
!
!    You should have received a copy of the GNU Lesser General Public License
!    along with ELPA.  If not, see <http://www.gnu.org/licenses/>
!
!    ELPA reflects a substantial effort on the part of the original
!    ELPA consortium, and we ask you to respect the spirit of the
!    license that we chose: i.e., please contribute any changes you
!    may have back to the original ELPA library distribution, and keep
!    any derivatives of ELPA under the same license that we chose for
!    the original distribution, the GNU Lesser General Public License.
!
!
#include "config-f90.h"
!>
!> Fortran test programm to demonstrates the use of
!> ELPA 2 real case library.
!> If "HAVE_REDIRECT" was defined at build time
!> the stdout and stderr output of each MPI task
!> can be redirected to files if the environment
!> variable "REDIRECT_ELPA_TEST_OUTPUT" is set
!> to "true".
!>
!> By calling executable [arg1] [arg2] [arg3] [arg4]
!> one can define the size (arg1), the number of
!> Eigenvectors to compute (arg2), and the blocking (arg3).
!> If these values are not set default values (4000, 1500, 16)
!> are choosen.
!> If these values are set the 4th argument can be
!> "output", which specifies that the EV's are written to
!> an ascii file.
!>
!> The real ELPA 2 kernel is set as the default kernel.
!> However, this can be overriden by setting
!> the environment variable "REAL_ELPA_KERNEL" to an
!> appropiate value.
!>
program test_real2

!-------------------------------------------------------------------------------
! Standard eigenvalue problem - REAL version
!
! This program demonstrates the use of the ELPA module
! together with standard scalapack routines
!
! Copyright of the original code rests with the authors inside the ELPA
! consortium. The copyright of any additional modifications shall rest
! with their original authors, but shall adhere to the licensing terms
! distributed along with the original code in the file "COPYING".
!
!-------------------------------------------------------------------------------
   use precision
   use ELPA1
   use ELPA2
   use elpa_utilities, only : error_unit
#ifdef WITH_OPENMP
   use test_util
#endif

   use mod_read_input_parameters
   use mod_check_correctness
   use mod_setup_mpi
   use mod_blacs_infrastructure
   use mod_prepare_matrix

#ifdef HAVE_REDIRECT
  use redirect
#endif
#ifdef HAVE_DETAILED_TIMINGS
 use timings
#endif
   implicit none
   include 'mpif.h'

   !-------------------------------------------------------------------------------
   ! Please set system size parameters below!
   ! na:   System size
   ! nev:  Number of eigenvectors to be calculated
   ! nblk: Blocking factor in block cyclic distribution
   !-------------------------------------------------------------------------------

   integer(kind=ik)           :: nblk
   integer(kind=ik)           :: na, nev

   integer(kind=ik)           :: np_rows, np_cols, na_rows, na_cols

   integer(kind=ik)           :: myid, nprocs, my_prow, my_pcol, mpi_comm_rows, mpi_comm_cols
   integer(kind=ik)           :: i, mpierr, my_blacs_ctxt, sc_desc(9), info, nprow, npcol

   integer, external          :: numroc

   real(kind=rk), allocatable :: a(:,:), z(:,:), tmp1(:,:), tmp2(:,:), as(:,:), ev(:)

   integer(kind=ik)           :: iseed(4096) ! Random seed, size should be sufficient for every generator
   integer(kind=ik)           :: STATUS
#ifdef WITH_OPENMP
   integer(kind=ik)           :: omp_get_max_threads,  required_mpi_thread_level, provided_mpi_thread_level
#endif
   logical                    :: write_to_file
   logical                    :: success

   success = .true.

   call read_input_parameters(na, nev, nblk, write_to_file)

   !-------------------------------------------------------------------------------
   !  MPI Initialization
   call setup_mpi(myid, nprocs)

   STATUS = 0
#ifdef WITH_OPENMP
   if (myid .eq. 0) then
      print *,"Threaded version of test program"
      print *,"Using ",omp_get_max_threads()," threads"
      print *," "
   endif
#endif

#ifdef HAVE_REDIRECT
   if (check_redirect_environment_variable()) then
     if (myid .eq. 0) then
       print *," "
       print *,"Redirection of mpi processes is used"
       print *," "
       if (create_directories() .ne. 1) then
         write(error_unit,*) "Unable to create directory for stdout and stderr!"
         stop
       endif
     endif
     call MPI_BARRIER(MPI_COMM_WORLD, mpierr)
     call redirect_stdout(myid)
   endif
#endif

   if (myid .eq. 0) then
      print *," "
      print *,"This ELPA2 is build with"
#ifdef WITH_REAL_AVX_BLOCK2_KERNEL
      print *,"AVX optimized kernel (2 blocking) for real matrices"
#endif
#ifdef WITH_REAL_AVX_BLOCK4_KERNEL
      print *,"AVX optimized kernel (4 blocking) for real matrices"
#endif
#ifdef WITH_REAL_AVX_BLOCK6_KERNEL
      print *,"AVX optimized kernel (6 blocking) for real matrices"
#endif

#ifdef WITH_REAL_GENERIC_KERNEL
     print *,"GENERIC kernel for real matrices"
#endif
#ifdef WITH_REAL_GENERIC_SIMPLE_KERNEL
     print *,"GENERIC SIMPLE kernel for real matrices"
#endif
#ifdef WITH_REAL_SSE_KERNEL
     print *,"SSE ASSEMBLER kernel for real matrices"
#endif
#ifdef WITH_REAL_BGP_KERNEL
     print *,"BGP kernel for real matrices"
#endif
#ifdef WITH_REAL_BGQ_KERNEL
     print *,"BGQ kernel for real matrices"
#endif
   endif
   if (write_to_file) then
     if (myid .eq. 0) print *,"Writing output files"
   endif

#ifdef HAVE_DETAILED_TIMINGS

   ! initialise the timing functionality

#ifdef HAVE_LIBPAPI
   call timer%measure_flops(.true.)
#endif

   call timer%measure_allocated_memory(.true.)
   call timer%measure_virtual_memory(.true.)
   call timer%measure_max_allocated_memory(.true.)

   call timer%set_print_options(&
#ifdef HAVE_LIBPAPI
                print_flop_count=.true., &
                print_flop_rate=.true., &
#endif
                print_allocated_memory = .true. , &
                print_virtual_memory=.true., &
                print_max_allocated_memory=.true.)


  call timer%enable()

  call timer%start("program")
#endif

   !-------------------------------------------------------------------------------
   ! Selection of number of processor rows/columns
   ! We try to set up the grid square-like, i.e. start the search for possible
   ! divisors of nprocs with a number next to the square root of nprocs
   ! and decrement it until a divisor is found.

   do np_cols = NINT(SQRT(REAL(nprocs))),2,-1
      if(mod(nprocs,np_cols) == 0 ) exit
   enddo
   ! at the end of the above loop, nprocs is always divisible by np_cols

   np_rows = nprocs/np_cols

   if(myid==0) then
      print *
      print '(a)','Standard eigenvalue problem - REAL version'
      print *
      print '(3(a,i0))','Matrix size=',na,', Number of eigenvectors=',nev,', Block size=',nblk
      print '(3(a,i0))','Number of processor rows=',np_rows,', cols=',np_cols,', total=',nprocs
      print *
   endif

   !-------------------------------------------------------------------------------
   ! Set up BLACS context and MPI communicators
   !
   ! The BLACS context is only necessary for using Scalapack.
   !
   ! For ELPA, the MPI communicators along rows/cols are sufficient,
   ! and the grid setup may be done in an arbitrary way as long as it is
   ! consistent (i.e. 0<=my_prow<np_rows, 0<=my_pcol<np_cols and every
   ! process has a unique (my_prow,my_pcol) pair).

   call set_up_blacsgrid(mpi_comm_world, my_blacs_ctxt, np_rows, np_cols, &
                         nprow, npcol, my_prow, my_pcol)

   if (myid==0) then
     print '(a)','| Past BLACS_Gridinfo.'
   end if

   ! All ELPA routines need MPI communicators for communicating within
   ! rows or columns of processes, these are set in get_elpa_communicators.

   mpierr = get_elpa_communicators(mpi_comm_world, my_prow, my_pcol, &
                                   mpi_comm_rows, mpi_comm_cols)

   if (myid==0) then
     print '(a)','| Past split communicator setup for rows and columns.'
   end if

   call set_up_blacs_descriptor(na ,nblk, my_prow, my_pcol, np_rows, np_cols, &
                                na_rows, na_cols, sc_desc, my_blacs_ctxt, info)

   if (myid==0) then
     print '(a)','| Past scalapack descriptor setup.'
   end if

   !-------------------------------------------------------------------------------
   ! Allocate matrices and set up a test matrix for the eigenvalue problem
#ifdef HAVE_DETAILED_TIMINGS
   call timer%start("set up matrix")
#endif
   allocate(a (na_rows,na_cols))
   allocate(z (na_rows,na_cols))
   allocate(as(na_rows,na_cols))

   allocate(ev(na))

   call prepare_matrix(na, myid, sc_desc, iseed,  a, z, as)

#ifdef HAVE_DETAILED_TIMINGS
   call timer%stop("set up matrix")
#endif
   ! set print flag in elpa1
   elpa_print_times = .true.

   !-------------------------------------------------------------------------------
   ! Calculate eigenvalues/eigenvectors

   if (myid==0) then
     print '(a)','| Entering two-stage ELPA solver ... '
     print *
   end if

   call mpi_barrier(mpi_comm_world, mpierr) ! for correct timings only
   success = solve_evp_real_2stage(na, nev, a, na_rows, ev, z, na_rows,  nblk, na_cols, &
                              mpi_comm_rows, mpi_comm_cols, mpi_comm_world)

   if (.not.(success)) then
      write(error_unit,*) "solve_evp_real_2stage produced an error! Aborting..."
      call MPI_ABORT(mpi_comm_world, 1, mpierr)
   endif

   if (myid==0) then
     print '(a)','| Two-step ELPA solver complete.'
     print *
   end if

   if(myid == 0) print *,'Time transform to tridi :',time_evp_fwd
   if(myid == 0) print *,'Time solve tridi        :',time_evp_solve
   if(myid == 0) print *,'Time transform back EVs :',time_evp_back
   if(myid == 0) print *,'Total time (sum above)  :',time_evp_back+time_evp_solve+time_evp_fwd


   if(write_to_file) then
      if (myid == 0) then
         open(17,file="EVs_real2_out.txt",form='formatted',status='new')
         do i=1,na
            write(17,*) i,ev(i)
         enddo
         close(17)
      endif
   endif
   !-------------------------------------------------------------------------------
   ! Test correctness of result (using plain scalapack routines)
   allocate(tmp1(na_rows,na_cols))
   allocate(tmp2(na_rows,na_cols))

   status = check_correctness(na, nev, as, z, ev, sc_desc, myid, tmp1, tmp2)

   deallocate(a)
   deallocate(as)

   deallocate(z)
   deallocate(tmp1)
   deallocate(tmp2)
   deallocate(ev)

#ifdef HAVE_DETAILED_TIMINGS
   call timer%stop("program")
   print *," "
   print *,"Timings program:"
   call timer%print("program")
   print *," "
   print *,"End timings program"
#endif
   call blacs_gridexit(my_blacs_ctxt)
   call mpi_finalize(mpierr)
   call EXIT(STATUS)
end

!-------------------------------------------------------------------------------