From 8835b95719cb072519a66d16599141eab8d592ca Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Thu, 3 Feb 2022 16:26:41 +0100
Subject: [PATCH] comment

---
 libsolutil/LP.cpp | 3 +++
 libsolutil/LP.h   | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/libsolutil/LP.cpp b/libsolutil/LP.cpp
index 640d30334..c6d3915fe 100644
--- a/libsolutil/LP.cpp
+++ b/libsolutil/LP.cpp
@@ -760,6 +760,9 @@ pair<LPResult, map<string, rational>> LPSolver::check(SolvingState _state)
 
 		LPResult lpResult;
 		vector<rational> solution;
+		// TODO this actually compares including the variable names.
+		// If we only compare based on coefficients, we will get way more cache hits.
+		// The downside is that we need to adjust the model.
 		auto it = m_cache.find(split);
 		if (it != m_cache.end())
 			tie(lpResult, solution) = it->second;
diff --git a/libsolutil/LP.h b/libsolutil/LP.h
index 22cfea036..9fb0ef943 100644
--- a/libsolutil/LP.h
+++ b/libsolutil/LP.h
@@ -161,6 +161,8 @@ public:
 
 private:
 	// TODO check if the model is requested in production. If not, we do not need to cache it.
+	// TODO This cache is inefficient because it compares including the variable names.
+	// See comment in LPSolver::check for details.
 	std::map<SolvingState, std::pair<LPResult, std::vector<boost::rational<bigint>>>> m_cache;
 };