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

icgstab
2bicgstab
Purpose BiConjugate Gradients Stabilized method
Syntax x = bicgstab(A,b)
bicgstab(A,b,tol)
bicgstab(A,b,tol,maxit)
bicgstab(A,b,tol,maxit,M)
bicgstab(A,b,tol,maxit,M1,M2)
bicgstab(A,b,tol,maxit,M1,M2,x0)
bicgstab(afun,b,tol,maxit,m1fun,m2fun,x0,p1,p2,...)
[x,flag] = bicgstab(A,b,...)
[x,flag,relres] = bicgstab(A,b,...)
[x,flag,relres,iter] = bicgstab(A,b,...)
[x,flag,relres,iter,resvec] = bicgstab(A,b,...)
Description x = bicgstab(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.
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If bicgstab converges, a message to that effect is displayed. If bicgstab 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.
bicgstab(A,b,tol) specifies the tolerance of the method. If tol is [], then
bicgstab uses the default, 1e-6.
bicgstab(A,b,tol,maxit) specifies the maximum number of iterations. If
maxit is [], then bicgstab uses the default, min(n,20).
bicgstab(A,b,tol,maxit,M) and bicgstab(A,b,tol,maxit,M1,M2) use
preconditioner M or M = M1*M2 and effectively solve the system
inv(M)*A*x = inv(M)*b for x. If M is [] then bicgstab applies no
preconditioner. M can be a function that returns M\x.
bicgstab(A,b,tol,maxit,M1,M2,x0) specifies the initial guess. If x0 is [],
then bicgstab uses the default, an all zero vector.