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/* Copyright 2019 David Grote
*
* This file is part of WarpX.
*
* License: BSD-3-Clause-LBNL
*/
/* -------------------------------------------------------------------------
! program to calculate the first zeroes (root abscissas) of the first
! kind bessel function of integer order n using the subroutine rootj.
! --------------------------------------------------------------------------
! sample run:
!
! (calculate the first 10 zeroes of 1st kind bessel function of order 2).
!
! zeroes of bessel function of order: 2
!
! number of calculated zeroes: 10
!
! table of root abcissas (5 items per line)
! 5.135622 8.417244 11.619841 14.795952 17.959819
21.116997 24.270112 27.420574 30.569204 33.716520
!
! table of error codes (5 items per line)
! 0 0 0 0 0
! 0 0 0 0 0
!
! --------------------------------------------------------------------------
! reference: from numath library by tuan dang trong in fortran 77
! [bibli 18].
!
! c++ release 1.0 by j-p moreau, paris
! (www.jpmoreau.fr)
! ------------------------------------------------------------------------ */
#ifndef WARPX_BESSEL_ROOTS_H_
#define WARPX_BESSEL_ROOTS_H_
#include <AMReX_REAL.H>
#include <AMReX_Vector.H>
/*----------------------------------------------------------------------
* calculate the first nk zeroes of bessel function j(n, x)
* including the trivial root (when n > 0)
*
* inputs:
* n order of function j (integer >= 0) i*4
* nk number of first zeroes (integer > 0) i*4
* outputs:
* roots(nk) table of first zeroes (abcissas) r*8
* ier(nk) table of error codes (must be zeroes) i*4
*
* reference :
* abramowitz m. & stegun irene a.
* handbook of mathematical functions
*/
void GetBesselRoots(int n, int nk, amrex::Vector<amrex::Real>& roots, amrex::Vector<int> &ier);
#endif // WARPX_BESSEL_ROOTS_H_
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