PRACE NPT

      Subroutine btrans ( n1, n2, ar, ai, tr, ti )

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

! --- 'btrans' performs a blockwise local transposition. Input

!     array is 'a[r|i]', output array is 't[r|i]'

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

      Use         numerics

      Use         mpi_module ! Contains #procs and sizes.

      Implicit    None

      Integer  :: n1, n2

      Real(l_) :: ar(n1*n2), ai(n1*n2), tr(n1*n2), ti(n1*n2)

      Integer  :: m1, m2, b1, b2, i, j, k, l

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

      m2 = sizes(me,1) ! <-- From mpi_module.

      b1 = 0; l = 1

      Do k = 0, nodes - 1

         m1 = sizes(k,2)

         b2 = 0

         Do i = 1, m2

            Do j = 1, m1

               tr(j+b1+b2) = ar(l)

               ti(j+b1+b2) = ai(l)

               l = l + 1

            End Do

            b2 = b2 + n2

         End Do

         b1 = b1 + m1

      End Do

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

      End Subroutine btrans