From 0c1603e15e4152f62f4b9d97665b5591ee271167 Mon Sep 17 00:00:00 2001
From: Michael Votaw <mjvotaw@gmail.com>
Date: Mon, 3 Mar 2025 19:24:57 -0600
Subject: [PATCH] Round bpm and beat to 3 decimal places using std::round()
 instead of just truncating to 3 decimal places (fixes discrepancy in GS hash
 generation)

---
 src/RageUtil.cpp | 10 ++++++++++
 src/RageUtil.h   |  3 ++-
 src/Steps.cpp    |  9 +++------
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/RageUtil.cpp b/src/RageUtil.cpp
index dc37a2d137..d3f5c313f3 100644
--- a/src/RageUtil.cpp
+++ b/src/RageUtil.cpp
@@ -19,6 +19,7 @@
 #include <cstdint>
 #include <ctime>
 #include <functional>
+#include <iomanip>
 #include <map>
 #include <numeric>
 #include <sstream>
@@ -370,6 +371,15 @@ RString FormatNumberAndSuffix( int i )
 	return NUM_PREFIX.GetValue() + ssprintf("%i", i) + sSuffix;
 }
 
+RString NormalizeDecimal(float num)
+{
+	float mult = 1000.0f;
+	float rounded = std::round(num * mult) / mult;
+	std::ostringstream os;
+	os << std::fixed << std::setprecision(3) << rounded;
+	return os.str();
+}
+
 struct tm GetLocalTime()
 {
 	const time_t t = time(nullptr);
diff --git a/src/RageUtil.h b/src/RageUtil.h
index b50f4fbea1..d9b9321d46 100644
--- a/src/RageUtil.h
+++ b/src/RageUtil.h
@@ -349,7 +349,8 @@ inline RString PrettyPercent( int fNumerator, int fDenominator ) { return Pretty
 RString Commify( int iNum );
 RString Commify(const RString& num, const RString& sep= ",", const RString& dot= ".");
 RString FormatNumberAndSuffix( int i );
-
+/* Round num to 3 decimal places and return as string with 3 decimal places */
+RString NormalizeDecimal(float num);
 
 struct tm GetLocalTime();
 
diff --git a/src/Steps.cpp b/src/Steps.cpp
index 2d9806d9cb..10c90cd912 100644
--- a/src/Steps.cpp
+++ b/src/Steps.cpp
@@ -32,7 +32,6 @@
 #include <algorithm>
 #include <cstddef>
 #include <vector>
-#include <iomanip>
 #include <regex>
 
 #include "StepParityGenerator.h"
@@ -805,16 +804,14 @@ void Steps::CalculateGrooveStatsHash(bool forceRecalculate)
 	TimingData * timingData = this->GetTimingData();
 	std::vector<TimingSegment *> segments = timingData->GetTimingSegments(SEGMENT_BPM);
 	std::vector<RString> bpmStrings;
+	bpmStrings.reserve(segments.size());
 	for (TimingSegment *segment : segments)
 	{
 		BPMSegment *bpmSegment = ToBPM(segment);
 		float beat = bpmSegment->GetBeat();
 		float bpm = bpmSegment->GetBPM();
-		std::ostringstream os;
-		os << std::fixed << std::setprecision(3) << beat;
-		os << "=";
-		os << std::fixed << std::setprecision(3) << bpm;
-		bpmStrings.push_back(os.str());
+		RString segmentStr = ssprintf("%s=%s", NormalizeDecimal(beat).c_str(), NormalizeDecimal(bpm).c_str());
+		bpmStrings.push_back(segmentStr);
 	}
 	RString bpmString = join(",", bpmStrings);