From 0592b6d86aad189dc99298227a1562773cb6d41f Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Fri, 1 Apr 2022 13:14:40 +0200
Subject: [PATCH] Small opt in pivot.

---
 libsolutil/LP.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libsolutil/LP.cpp b/libsolutil/LP.cpp
index 36deb7bc9..fceac6fac 100644
--- a/libsolutil/LP.cpp
+++ b/libsolutil/LP.cpp
@@ -203,6 +203,8 @@ void performPivot(Tableau& _tableau, size_t _pivotRow, size_t _pivotColumn)
 	auto subtractMultipleOfPivotRow = [&](LinearExpression& _row) {
 		if (_row[_pivotColumn] == rational{1})
 			_row -= _pivotRowData;
+		else if (_row[_pivotColumn] == rational{-1})
+			_row += _pivotRowData;
 		else if (_row[_pivotColumn])
 			_row -= _row[_pivotColumn] * _pivotRowData;
 	};