qmr - quasi minimal resiqual method with preconditioning

Calling Sequence

[x,flag,err,iter,res] = qmr(A,b,x0,M1,M1p,M2,M2p,maxi,tol)

Parameters

• A : matrix of size n-by-n or function returning A*x
• b : right hand side vector
• x0 : initial guess vector (default: zeros(n,1))
• M1 : left preconditioner: matrix or function returning M1*x (In the first case, default: eye(n,n))
• M1p : must only be provided when M1 is a function. In this case M1p is the function which returns M1'*x
• M2 : right preconditioner: matrix or function returning M2*x (In the first case, default: eye(n,n))
• M2p : must only be provided when M2 is a function. In this case M2p is the function which returns M2'*x
• maxi : maximum number of iterations (default: n)
• tol : error tolerance (default: 1000*%eps)
• x : solution vector
• flag : 0 = qmr converged to the desired tolerance within maxi iterations
• res : residual vector
• err : final residual norm
• iter : number of iterations performed

Description

Solves the linear system Ax=b using the Quasi Minimal Residual Method with preconditioning.

See Also

gmres ,  

Author

SAGE Group, IRISA 2005