multigrid_setup.m

五点差分型多重网格方法：各种插值算子的比较）

%MULTIGRID_SETUP Generate the linear systems for the coarse multigrid levels
%
%       MULTIGRID_SETUP generates the coarse-grid linear systems for the 
%       currently defined problem.
%
%       Accesses global variables in "include_flags"
%       Accesses global variables in "include_globals"

function multigrid_setup

include_flags
include_globals

[X1,Y1] = meshgrid([0:nx1]/nx1,[0:ny1]/ny1);
ARRAY1 = zeros(nx1+1, ny1+1); 

if coarse_level >= 2
   nx2 = nx1/2 ;
   ny2 = ny1/2 ;
   [x2,y2,A2,N2,bb] = get_matrix_fem(nx2,ny2);
   [X2,Y2] = meshgrid([0:nx2]/nx2,[0:ny2]/ny2);
   if interp_flag == EXPLICIT_BILINEAR
      ARRAY1 = sp_prolong(nx1,ny1,nx2,ny2);
   else
      ARRAY2 = zeros(nx2+1, ny2+1);
   end
end

if coarse_level >= 3
   nx3 = nx2/2;
   ny3 = ny2/2;
   [x3,y3,A3,N3,bb] = get_matrix_fem(nx3,ny3);
   [X3,Y3] = meshgrid([0:nx3]/nx3,[0:ny3]/ny3);
   if interp_flag == EXPLICIT_BILINEAR
      ARRAY2 = sp_prolong(nx2,nx2,nx3,nx3);
   else
      ARRAY3 = zeros(nx3+1, ny3+1);
   end
end

if coarse_level >= 4
   nx4 = nx3/2 ;
   ny4 = ny3/2 ;
   [x4,y4,A4,N4,bb] = get_matrix_fem(nx4,ny4-1);
   [X4,Y4] = meshgrid([0:nx4]/nx4,[0:ny4]/ny4);
   if interp_flag == EXPLICIT_BILINEAR
      ARRAY3 = sp_prolong(nx3,nx3,nx4,nx4);
   else
      ARRAY4 = zeros(nx4+1,ny4+1);
   end
end

if coarse_level >= 5
   nx5 = (nx4+1)/2 - 1;
   ny5 = (ny4+1)/2 - 1;
   [x5,y5,A5,N5,bb] = get_matrix_fem(nx5-1,nx5-1);
   [X5,Y5] = meshgrid([0:nx5]/nx5,[0:ny5]/ny5);
   if interp_flag == EXPLICIT_BILINEAR
      ARRAY4 = sp_prolong(nx4,nx4,nx5,nx5); 
   else
      ARRAY5 = zeros(nx5+1,ny5+1);
   end
end