From 092d947830408475b65cbc63b2b5a6c733cb3435 Mon Sep 17 00:00:00 2001
From: Kp <kp@valhallalegends.com>
Date: Sun, 15 Jan 2017 00:03:14 +0000
Subject: [PATCH] Optimize change_light search

Use std::equal_range to find the upper and lower bounds in a single
binary search, rather than relying on a linear search to find the first
sought element.
---
 common/main/segment.h     |  8 ++++++++
 similar/main/gamesave.cpp |  9 +--------
 similar/main/gameseg.cpp  | 18 ++++++------------
 3 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/common/main/segment.h b/common/main/segment.h
index f5297eeb7..6069dcb35 100644
--- a/common/main/segment.h
+++ b/common/main/segment.h
@@ -279,6 +279,14 @@ struct dl_index {
 	uint8_t   sidenum;
 	uint8_t count;
 	uint16_t index;
+	bool operator<(const dl_index &rhs) const
+	{
+		if (segnum < rhs.segnum)
+			return true;
+		if (segnum > rhs.segnum)
+			return false;
+		return sidenum < rhs.sidenum;
+	}
 };
 #endif
 
diff --git a/similar/main/gamesave.cpp b/similar/main/gamesave.cpp
index 15e817b42..291f19a43 100644
--- a/similar/main/gamesave.cpp
+++ b/similar/main/gamesave.cpp
@@ -993,14 +993,7 @@ static int load_game_data(PHYSFS_File *LoadFile)
 		const auto &&lr = partial_range(Dl_indices, Num_static_lights);
 		range_for (auto &i, lr)
 			dl_index_read(&i, LoadFile);
-		const auto predicate = [](const dl_index &a, const dl_index &b) {
-			if (a.segnum < b.segnum)
-				return true;
-			if (a.segnum > b.segnum)
-				return false;
-			return a.sidenum < b.sidenum;
-		};
-		std::sort(lr.begin(), lr.end(), predicate);
+		std::sort(lr.begin(), lr.end());
 	}
 
 	//	Indicate that no light has been subtracted from any vertices.
diff --git a/similar/main/gameseg.cpp b/similar/main/gameseg.cpp
index 65566d815..65c9bdbac 100644
--- a/similar/main/gameseg.cpp
+++ b/similar/main/gameseg.cpp
@@ -1686,18 +1686,15 @@ static void change_segment_light(const vsegptridx_t segp,int sidenum,int dir)
 //	dir = -1 -> subtract light
 //	dir = 17 -> add 17x light
 //	dir =  0 -> you are dumb
-static void change_light(const vsegptridx_t segnum, int sidenum, int dir)
+static void change_light(const vsegptridx_t segnum, const uint8_t sidenum, const int dir)
 {
 	const fix ds = dir * DL_SCALE;
-	range_for (auto &i, partial_const_range(Dl_indices, Num_static_lights))
+	const auto &&pr = partial_const_range(Dl_indices, Num_static_lights);
+	const auto &&er = std::equal_range(pr.begin(), pr.end(), dl_index{segnum, sidenum, 0, 0});
+	range_for (auto &i, partial_range_t<const dl_index *>(er.first, er.second))
 	{
-		if (i.segnum == segnum)
-		{
-			if (i.sidenum > sidenum)
-				break;
-			if (i.sidenum < sidenum)
-				continue;
-			range_for (auto &j, partial_const_range(Delta_lights, static_cast<uint_fast32_t>(i.index), static_cast<uint_fast32_t>(i.count)))
+		const uint_fast32_t idx = i.index;
+			range_for (auto &j, partial_const_range(Delta_lights, idx, idx + i.count))
 			{
 				assert(j.sidenum < MAX_SIDES_PER_SEGMENT);
 				const auto &&segp = vsegptr(j.segnum);
@@ -1709,9 +1706,6 @@ static void change_light(const vsegptridx_t segnum, int sidenum, int dir)
 						l = 0;
 				}
 			}
-		}
-		else if (i.segnum > segnum)
-			break;
 	}
 
 	//recompute static light for segment