From e528fabbe4e841f5c4ea9d61d2e47c312a96f4f9 Mon Sep 17 00:00:00 2001
From: EvilSpirit <anandamide@mail.ru>
Date: Thu, 23 Dec 2021 10:14:27 -0600
Subject: [PATCH] Add an early out in writing jacobian.

Split from previous large 'Eigen library integration' commit.
---
 src/system.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/system.cpp b/src/system.cpp
index c93b0a16..00f84c45 100644
--- a/src/system.cpp
+++ b/src/system.cpp
@@ -63,6 +63,8 @@ bool System::WriteJacobian(int tag) {
             if(j == paramToIndex.end()) continue;
             Expr *pd = f->PartialWrt(p);
             pd = pd->FoldConstants();
+            if(pd->IsZeroConst())
+                continue;
             mat.A.sym[i][j->second] = pd;
         }
         paramsUsed.Clear();