For the cases IGRSW=11 and IGRSW=12, GPHPLT plots the convergence history of other iterations implemented in PLTMG which are sometimes of interest. For the case IGRSW=11, the convergence history for the function
which measures the increment to the singular vector
as a function of
inverse iteration index k.
(since these vectors are always normalized to have unit length
in 
, we need not consider the relative change).
If ISPD=0 then the displayed quantity is the larger of the changes in
the left and right singular vectors.
For the case IGRSW=12, GPHPLT displays the convergence of the
upper and lower bounds for the guarded secant/bisection iteration for computing
singular points, as described in Section 
.
In particular, we graph the functions
Here 
and 
are the singular values at the
upper and lower bounds of the interval (in 
)
known to contain 
. In the graph,
iterates for the upper bound are marked with
red triangles, and iterates for the lower bound are marked with blue triangles.
Figure: GPHPLT output for IGRSW=2.