LS_tol sets the residual reduction for the linear solver of the correction equation.

If LS_tol is a positive real then the correction equation is solved with a residual reduction of LS_tol in each Jacobi-Davidson step.

If LS_tol is a row [a₁,a₂,...,a_p] of positive reals then the correction equation at the ith Jacobi-Davidson step is solved with a residual reduction of a_i provided that i<=p. If i=p+j then the residual reduction at the ith Jacobi-Davidson step is a_p*b^j where b=a_p/a_p-1. i is reset to 0 when a Schur vector is detected.

The required residual reduction is not obtained if the maximum number LS_MaxIt of iteration steps of the linear solver is reached before.

The default for LS_MaxIt is [1,0.7] if a preconditioner is used (then a_i=0.7^i-1). In the other case, the default is [0.7,0.49] (then a_i=0.7ⁱ).

Gerard L. G. Sleijpen© sleijpen@math.ruu.nl

Last update: April 8 1999