V-cycle Multigrid method for 2D Poisson Equation,代码写得很清楚,是非常好的学习材料
1)如何编译运行 rm -f a.out
gfortran -O3 poisson2d_MG.f90
./a.out
!----------------------! !Solver: !----------------------! isolver = 1 if (isolver.eq.0) then !Gauss-Seidel scheme call GS(nx,ny,dx,dy,f,u,tol) else call MG5(nx,ny,dx,dy,f,u,tol) end if
这个地方修改isolver = 0 可以转化成Gauss-Seidel迭代
3)
ireo = 2
if (ireo.eq.1) then !simply injection
do i=1,nxh-1
do j=1,nyh-1
f(i,j) = r(2*i,2*j)
end do
end do
else if (ireo.eq.2) then !half-weight
do i=1,nxh-1
do j=1,nyh-1
f(i,j) = 1.0d0/8.0d0*( 4.0d0*r(2*i,2*j) &
+ 1.0d0*(r(2*i+1,2*j)+r(2*i-1,2*j)+r(2*i,2*j+1)+r(2*i,2*j-1)) )
end do
end do
else !full-weight (trapezoidal)
do i=1,nxh-1 do j=1,nyh-1 f(i,j) = 1.0d0/16.0d0*( 4.0d0r(2i,2j) & + 2.0d0(r(2i+1,2j)+r(2i-1,2j)+r(2i,2j+1)+r(2i,2j-1)) & + 1.0d0*(r(2i+1,2j+1)+r(2i-1,2j-1)+r(2i-1,2j+1)+r(2i+1,2j-1))) end do end do
修改ireo可以换不现的f2c的插值方式,但是效果都差不多。