MATLAB Function Reference Volume 1: A - E - Bad Request

icg
2bicg
Purpose BiConjugate Gradients method
Syntax x = bicg(A,b)
bicg(A,b,tol)
bicg(A,b,tol,maxit)
bicg(A,b,tol,maxit,M)
bicg(A,b,tol,maxit,M1,M2)
bicg(A,b,tol,maxit,M1,M2,x0)
bicg(afun,b,tol,maxit,mfun1,mfun2,x0,p1,p2,...)
[x,flag] = bicg(A,b,...)
[x,flag,relres] = bicg(A,b,...)
[x,flag,relres,iter] = bicg(A,b,...)
[x,flag,relres,iter,resvec] = bicg(A,b,...)
Description x = bicg(A,b) attempts to solve the system of linear equations A*x = b for x.
The n-by-n coefficient matrix A must be square and the column vector b must
have length n. A can be a function afun such that afun(x) returns A*x and
afun(x,'transp') returns A'*x.
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If bicg converges, a message to that effect is displayed. If bicg fails to converge
after the maximum number of iterations or halts for any reason, a warning
message is printed displaying the relative residual norm(b-A*x)/norm(b) and
the iteration number at which the method stopped or failed.
bicg(A,b,tol specifies the tolerance of the method. If tol is [], then bicg
uses the default, 1e-6.
bicg(A,b,tol,maxit) specifies the maximum number of iterations. If maxit
is [], then bicg uses the default, min(n,20).
bicg(A,b,tol,maxit,M) and bicg(A,b,tol,maxit,M1,M2) use the
preconditioner M or M = M1*M2 and effectively solve the system
inv(M)*A*x = inv(M)*b for x. IfM is [] then bicg applies no preconditioner.
M can be a function mfun such that mfun(x) returns M\x and mfun(x,'transp')
returns M'\x.
bicg(A,b,tol,maxit,M1,M2,x0) specifies the initial guess. If x0 is [], then
bicg uses the default, an all-zero vector.