lapacienprecon.edp

FreeFem++可以生成高质量的有限元网格。可以用于流体力学

// Warning we forgot to remove 3 pointer in this exemple
// precon=Precon correct in version 1.26 
verbosity=4;

mesh Th=square(10,10,[10*x,5*y]);
fespace Vh(Th,P1);

Vh u,v;

u=0;
func f= 0;
func g= 5*x+y;
int i=0;
real error=0.1, coef= 0.1^(1./5.);

func real[int]  Precon(real[int] & xx)
{
// cout << xx[0] << " -----" ;
  xx[0]=1001;
  return xx;
};

problem Probem1(u,v,solver=CG,init=i,eps=-1.0e-6,precon=Precon) =
    int2d(Th)(  dx(u)*dx(v) + dy(u)*dy(v)) 
  + int1d(Th,1) ( u*v ) 
  + int2d(Th) ( v*f ) 
  + int1d(Th,2) (-5*v)
  + int1d(Th,1) ( (+1-g)*v)
  + on(3,4,u=g)  ;
  
real cpu=clock();
Probem1; // SOLVE THE PROBLEM 1
plot(u);
cout << " CPU = " << clock()-cpu << endl;