BUG: resolve issue #1313 | stabilise SVDinv

src/OpenFOAM/matrices/scalarMatrices/scalarMatrices.C

@@ -329,6 +329,14 @@ Foam::scalarRectangularMatrix Foam::SVDinv
     scalar minCondition
 )
 {
+    if (minCondition < SMALL)
+    {
+        WarningInFunction
+            << "Input cutoff for small singular values = " << minCondition
+            << " may be destabilising, hence reset to SMALL" << nl;
+
+        minCondition = max(minCondition, SMALL);
+    }
     SVD svd(A, minCondition);
     return svd.VSinvUt();
 }