NOPRECON — Do not use preconditioning during conjugate gradient.
PSOLVE=CGDMS and PSOLVE=QNDMS use a preconditioned gradient for the search direction during the conjugate gradient step. The preconditioning uses the inverse of the diagonal Hessian matrix and hence is a quasi-Newton step. In rare cases, this preconditioning may experience problems and may be disabled using the NOPRECON keyword.
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