From 140c76276a6cb5bfad89f84afb6c618be4810d2d Mon Sep 17 00:00:00 2001
From: "Pavel N. Krivitsky" <p.krivitsky@unsw.edu.au>
Date: Fri, 26 Jan 2024 19:48:40 +1100
Subject: [PATCH] In ergm.MCMLE() for missing data, guard against constrained
 variance being higher than unconstrained on a particular interation by
 treating the difference as 0 instead.

---
 R/ergm.MCMLE.R | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/R/ergm.MCMLE.R b/R/ergm.MCMLE.R
index a205f1094..406c93be8 100644
--- a/R/ergm.MCMLE.R
+++ b/R/ergm.MCMLE.R
@@ -315,6 +315,8 @@ ergm.MCMLE <- function(init, s, s.obs,
       estdiff <- NVL3(esteq.obs, colMeans(.), 0) - colMeans(esteq)
       pprec <- diag(sqrt(control$MCMLE.MCMC.precision), nrow=length(estdiff))
       Vm <- pprec%*%(cov(esteq) - NVL3(esteq.obs, cov(.), 0))%*%pprec
+      novar <- diag(Vm) <= 0
+      Vm[,novar] <- Vm[novar,] <- 0
       d2 <- xTAx_seigen(estdiff, Vm)
       if(d2<2) last.adequate <- TRUE
     }