From 9f2077b1f38a0ca17b01c991411ac51c7132022f Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Thu, 23 May 2019 19:40:32 +0000
Subject: [PATCH] Explain how forceDofCheck in System::Solve works. NFC.

---
 src/system.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/system.cpp b/src/system.cpp
index 85d439f..07cad70 100644
--- a/src/system.cpp
+++ b/src/system.cpp
@@ -418,6 +418,8 @@ SolveResult System::Solve(Group *g, int *dof, List<hConstraint> *bad,
     param.ClearTags();
     eq.ClearTags();
 
+    // Solving by substitution eliminates duplicate e.g. H/V constraints, which can cause rank test
+    // to succeed even on overdefined systems, which will fail later.
     if(!forceDofCheck) {
         SolveBySubstitution();
     }