int x0 = ipntr[1-1]-1; // Fortran is off-by-one compared to Java!
int y0 = ipntr[2-1]-1;
Vector x = Vector.copy(workd, x0, n);
Vector y = this.callback(x);
assert y.size() == n;
y.storeOn(workd, y0);
}
/*
* Either we have convergence or there is an error.
*
*/