matrix.f90

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module matrix
  use neko_config, only : neko_bcknd_device
  use num_types, only : rp, xp
  use device, only : device_map, device_unmap, device_memcpy, &
       device_sync
  use device_math, only : device_copy, device_cfill
  use utils, only : neko_error, neko_varname_len
  use, intrinsic :: iso_c_binding
  implicit none
  private
 
  type, public :: matrix_t
     real(kind=rp), allocatable :: x(:,:) 
     character(len=NEKO_VARNAME_LEN) :: name = ""
     type(c_ptr) :: x_d = c_null_ptr 
     integer, private :: nrows = 0
     integer, private :: ncols = 0
     integer, private :: n = 0
   contains
     procedure, pass(m) :: init => matrix_init
     procedure, pass(m) :: free => matrix_free
     procedure, pass(m) :: size => matrix_size
     procedure, pass(m) :: copy_from => matrix_copy_from
     procedure, pass(m) :: get_nrows => matrix_nrows
     procedure, pass(m) :: get_ncols => matrix_ncols
     procedure, pass(m) :: matrix_assign_matrix
     procedure, pass(m) :: matrix_assign_scalar
     procedure, pass(m) :: inverse => matrix_bcknd_inverse
     procedure, pass(m) :: inverse_on_host => cpu_matrix_inverse
 
     generic :: assignment(=) => matrix_assign_matrix, &
          matrix_assign_scalar
 
     procedure, pass(m), private :: alloc => matrix_allocate
  end type matrix_t
 
  type, public :: matrix_ptr_t
     type(matrix_t), pointer :: ptr
  end type matrix_ptr_t
 
contains
 
  subroutine matrix_init(m, nrows, ncols, name)
    class(matrix_t), intent(inout) :: m
    integer, intent(in) :: nrows
    integer, intent(in) :: ncols
    character(len=*), intent(in), optional :: name
 
    ! m%alloc zeroes the device side (and synchronizes) before any
    ! host-side touch: under zero-copy the device then faults the
    ! pages (device first touch), which gives contiguous physical
    ! mappings and thus better GPU TLB utilisation; rewriting the
    ! zeros on the host afterwards is benign
    call m%alloc(nrows, ncols)
    m%x = 0.0_rp
 
    if (present(name)) then
       m%name = name
    end if
 
 
  end subroutine matrix_init
 
  subroutine matrix_allocate(m, nrows, ncols)
    class(matrix_t), intent(inout) :: m
    integer, intent(in) :: nrows
    integer, intent(in) :: ncols
 
    call m%free()
 
    allocate(m%x(nrows, ncols))
    m%nrows = nrows
    m%ncols = ncols
    m%n = nrows*ncols
 
    if (neko_bcknd_device .eq. 1) then
       call device_map(m%x, m%x_d, m%n)
       call device_cfill(m%x_d, 0.0_rp, m%n)
       call device_sync()
    end if
 
  end subroutine matrix_allocate
 
  subroutine matrix_free(m)
    class(matrix_t), intent(inout) :: m
 
    if (allocated(m%x)) then
       if (neko_bcknd_device .eq. 1) then
          call device_unmap(m%x, m%x_d)
       end if
       deallocate(m%x)
    end if
 
    m%nrows = 0
    m%ncols = 0
    m%n = 0
    m%name = ""
 
  end subroutine matrix_free
 
  pure function matrix_size(m) result(s)
    class(matrix_t), intent(in) :: m
    integer :: s
    s = m%n
  end function matrix_size
 
 
  subroutine matrix_copy_from(m, memdir, sync)
    class(matrix_t), intent(inout) :: m
    integer, intent(in) :: memdir
    logical, intent(in) :: sync
 
    if (neko_bcknd_device .eq. 1) then
       call device_memcpy(m%x, m%x_d, m%n, memdir, sync)
    end if
 
  end subroutine matrix_copy_from
 
  pure function matrix_nrows(m) result(nr)
    class(matrix_t), intent(in) :: m
    integer :: nr
    nr = m%nrows
  end function matrix_nrows
 
  pure function matrix_ncols(m) result(nc)
    class(matrix_t), intent(in) :: m
    integer :: nc
    nc = m%ncols
  end function matrix_ncols
 
  subroutine matrix_assign_matrix(m, w)
    class(matrix_t), intent(inout) :: m
    type(matrix_t), intent(in) :: w
 
    if (allocated(m%x)) then
       call m%free()
    end if
 
    if (.not. allocated(m%x)) then
 
       m%nrows = w%nrows
       m%ncols = w%ncols
       m%n = w%n
       allocate(m%x(m%nrows, m%ncols))
 
       if (neko_bcknd_device .eq. 1) then
          call device_map(m%x, m%x_d, m%n)
       end if
 
    end if
 
    if (neko_bcknd_device .eq. 1) then
       call device_copy(m%x_d, w%x_d, m%n)
    else
       m%x = w%x
    end if
 
    m%name = w%name
 
  end subroutine matrix_assign_matrix
 
  subroutine matrix_assign_scalar(m, s)
    class(matrix_t), intent(inout) :: m
    real(kind=rp), intent(in) :: s
 
    if (.not. allocated(m%x)) then
       call neko_error('matrix not allocated')
    end if
 
    if (neko_bcknd_device .eq. 1) then
       call device_cfill(m%x_d, s, m%n)
    else
       m%x = s
    end if
 
  end subroutine matrix_assign_scalar
 
  subroutine matrix_bcknd_inverse(m, bcknd)
    class(matrix_t), intent(inout) :: m
    integer, optional :: bcknd
 
    if (neko_bcknd_device .eq. 1 .and. &
         bcknd .eq. neko_bcknd_device) then
       call neko_error("matrix_bcknd_inverse not &
       &implemented on accelarators.")
    else
       call cpu_matrix_inverse(m)
    end if
 
  end subroutine matrix_bcknd_inverse
 
  subroutine cpu_matrix_inverse(m)
    ! Gauss-Jordan matrix inversion with full pivoting
    ! Num. Rec. p. 30, 2nd Ed., Fortran
    ! m%x     is an sqaure matrix
    ! rmult is m  work array of length nrows = ncols
    class(matrix_t), intent(inout) :: m
    integer :: indr(m%nrows), indc(m%ncols), ipiv(m%ncols)
    real(kind=xp) :: rmult(m%nrows), amx, tmp, piv, eps
    integer :: i, j, k, ir, jc
 
    if (.not. (m%ncols .eq. m%nrows)) then
       call neko_error("Fatal error: trying to invert m matrix that is not &
       &square")
    end if
 
    eps = 1e-9_rp
    ipiv = 0
 
    do k = 1, m%nrows
       amx = 0.0_rp
       do i = 1, m%nrows ! Pivot search
          if (ipiv(i) .ne. 1) then
             do j = 1, m%nrows
                if (ipiv(j) .eq. 0) then
                   if (abs(m%x(i, j)) .ge. amx) then
                      amx = abs(m%x(i, j))
                      ir = i
                      jc = j
                   end if
                else if (ipiv(j) .gt. 1) then
                   return
                end if
             end do
          end if
       end do
       ipiv(jc) = ipiv(jc) + 1
 
       !  Swap rows
       if (ir .ne. jc) then
          do j = 1, m%ncols
             tmp = m%x(ir, j)
             m%x(ir, j) = m%x(jc, j)
             m%x(jc, j) = tmp
          end do
       end if
       indr(k) = ir
       indc(k) = jc
 
       if (abs(m%x(jc, jc)) .lt. eps) then
          call neko_error("matrix_inverse error: small Gauss Jordan Piv")
       end if
       piv = 1.0_xp/m%x(jc, jc)
       m%x(jc, jc) = 1.0_xp
       do j = 1, m%ncols
          m%x(jc, j) = m%x(jc, j)*piv
       end do
 
       do j = 1, m%ncols
          tmp = m%x(jc, j)
          m%x(jc, j) = m%x(1 , j)
          m%x(1 , j) = tmp
       end do
       do i = 2, m%nrows
          rmult(i) = m%x(i, jc)
          m%x(i, jc) = 0.0_rp
       end do
 
       do j = 1, m%ncols
          do i = 2, m%nrows
             m%x(i, j) = m%x(i, j) - rmult(i)*m%x(1, j)
          end do
       end do
 
       do j = 1, m%ncols
          tmp = m%x(jc, j)
          m%x(jc, j) = m%x(1 , j)
          m%x(1 , j) = tmp
       end do
    end do
 
    ! Unscramble matrix
    do j = m%nrows, 1, -1
       if (indr(j) .ne. indc(j)) then
          do i = 1, m%nrows
             tmp = m%x(i, indr(j))
             m%x(i, indr(j)) = m%x(i, indc(j))
             m%x(i, indc(j)) = tmp
          end do
       end if
    end do
 
    return
  end subroutine cpu_matrix_inverse
 
end module matrix