## Copyright (C) 2004-2008  Carlo de Falco
##
## SECS2D - A 2-D Drift--Diffusion Semiconductor Device Simulator
##
## SECS2D is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or
## (at your option) any later version.
##
## SECS2D 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 General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with SECS2D; If not, see <http://www.gnu.org/licenses/>.
##
## AUTHOR: Carlo de Falco <cdf _AT_ users.sourceforge.net>

## -*- texinfo -*-
##
## @deftypefn {Function File}@
## {@var{p},@var{e},@var{t}} = Ustructmesh(@var{x},@var{y},@var{region},@var{sides})
##
## Compute PDE-tool like fields for structured mesh
##
## @end deftypefn

function [p,e,t]=Ustructmesh_random(x,y,region,sides)

  x       = sort(x);
  y       = sort(y);
  nx      = length(x);
  ny      = length(y);
  [XX,YY] = meshgrid(x,y);
  p       = [XX(:),YY(:)]';

  iiv (ny,nx) = 0;
  iiv(:)      = 1:nx*ny;
  iiv(end,:)  = [];
  iiv(:,end)  = [];
  iiv         = iiv(:)';

  niiv    = length(iiv);
  theperm = iiv(randperm(niiv));
  first   = theperm(1:floor(niiv/2));
  second  = theperm(floor(niiv/2)+1:end);

  t = [[first;first+ny;first+ny+1],[first;first+ny+1;first+1] ];
  t = [t,[second;second+ny;second+1],[second+ny;second+ny+1;second+1] ];

  t (4,:)=region;

  l1 = 1+ny*([1:nx]-1);
  l4 = 1:ny;
  l2 = ny*(nx-1)+1:nx*ny;
  l3 = ny + l1 -1;

  e = [ l1([1:end-1]) l2([1:end-1]) l3([1:end-1]) l4([1:end-1])
       l1([2:end]) l2([2:end]) l3([2:end]) l4([2:end])
       [l1([1:end-1]) l2([1:end-1]) l3([1:end-1]) l4([1:end-1])]*0
       [l1([1:end-1]) l2([1:end-1]) l3([1:end-1]) l4([1:end-1])]*0
       l1([1:end-1])*0+sides(1) l2([1:end-1])*0+sides(2) l3([1:end-1])*0+sides(3) l4([1:end-1])*0+sides(4)
       [l1([1:end-1]) l2([1:end-1]) l3([1:end-1]) l4([1:end-1])]*0
       [l1([1:end-1]) l2([1:end-1]) l3([1:end-1]) l4([1:end-1])]*0+region
       ];

endfunction