Conjugate gradient methods form a class of iterative algorithms that are highly effective for solving large‐scale unconstrained optimisation problems.

Here we propose an alternative method based on conjugate gradients. The key, as we show, is that the EM step can be viewed (approximately at least) as a generalized gradient, making it natural to ...

Vance Faber, Thomas Manteuffel, Necessary and Sufficient Conditions for the Existence of a Conjugate Gradient Method, SIAM Journal on Numerical Analysis, Vol. 21, No. 2 (Apr., 1984), pp. 352-362 ...