psfun_utils_mod.f90 Source File

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! Copyright (c) 2020, Fabio Durastante
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module psfun_utils_mod
  !! This modules contains some utility function that are used in the library.
  use psb_base_mod
  implicit none

  ! Fixed parameters
  real(psb_dpk_), private, parameter :: DPI = 4.0_psb_dpk_*ATAN(1.0_psb_dpk_) !! Double precision \(\pi\) for internal usage

  interface ellipkkp
    !! Complete elliptic integral of the first kind, with complement.
    !! Returns the value of the complete elliptic integral of the first kind,
    !! evaluated at \(M=\exp(-2\pi L)\), \(0 < L < \infty\), and the
    !! complementarity parameter \(1-M\).
      module function ellipkkp(L) result(K)
        real(psb_dpk_), intent(in)  :: L
        real(psb_dpk_)              :: K(2)
      end function
  end interface ellipkkp

  interface ellipj
    !! Returns the values of the Jacobi elliptic functions evaluated at `real`
    !! or `complex` argument u and parameter \(M = \exp(-2 \pi L)\),
    !! \(0 < L < \infty\). For \(M = K^2\), and \(K\) the elliptic modulus.
    module subroutine d_ellipj(u,L,sn,cn,dn)
      real(psb_dpk_), intent(in)    :: u
      real(psb_dpk_), intent(in)    :: L
      real(psb_dpk_), intent(out)   :: sn,cn,dn
    end subroutine
    recursive module subroutine z_ellipj(u,L,sn,cn,dn,flag)
      complex(psb_dpk_), intent(in)    :: u
      real(psb_dpk_), intent(in)       :: L
      complex(psb_dpk_), intent(out)   :: sn,cn,dn
      logical, optional, intent(in)    :: flag
    end subroutine
  end interface ellipj

  interface horner
    !! Apply Horner rule to evaluate a polynomial
    module function horner(coeffs, x) result (res)
      real(psb_dpk_), dimension (:), intent (in) :: coeffs !! Coefficient of the polynomial
      real(psb_dpk_), intent (in) :: x !! Where to evaluate
      real(psb_dpk_) :: res !! Result
    end function
  end interface horner

contains

end module psfun_utils_mod