From 8b74992e66cdde28617e5930d8d7608d5110b859 Mon Sep 17 00:00:00 2001
From: Andreas Huber <bitbucket@lucares.de>
Date: Sun, 24 Sep 2017 09:53:25 +0200
Subject: [PATCH] reduce memory allocations by 25% with a cache of formatted
 longs

---
 .../org/lucares/recommind/logs/Plotter.java   | 22 ++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
index f62d0eb..d550e50 100644
--- a/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
+++ b/pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java
@@ -38,6 +38,17 @@ public class Plotter {
 	private static final Logger METRICS_LOGGER = LoggerFactory.getLogger("org.lucares.metrics.plotter");
 
 	private static final String DEFAULT_GROUP = "<none>";
+	
+	private static final int INT_TO_STRING_CACHE_SIZE= 1000;
+	private static final String[] INT_TO_STRING;
+	static {
+		
+		INT_TO_STRING = new String[INT_TO_STRING_CACHE_SIZE];
+		
+		for (int i = 0; i < INT_TO_STRING_CACHE_SIZE; i++){
+			INT_TO_STRING[i] = String.valueOf(i);
+		}
+	}
 
 	private final PerformanceDb db;
 	private final Path tmpBaseDir;
@@ -234,7 +245,7 @@ public class Plotter {
 
 				if (fromEpochMilli <= entry.getEpochMilli() && entry.getEpochMilli() <= toEpochMilli) {
 					
-					final String value = String.valueOf(entry.getValue());
+					final String value = longToString(entry.getValue());
 					final String formattedDate;
 					
 					if (useMillis){
@@ -261,4 +272,13 @@ public class Plotter {
 		METRICS_LOGGER.debug("wrote {} values to csv in: {}ms (ignored {} values) use millis: {}", count, (System.nanoTime() - start) / 1_000_000.0, ignoredValues, Boolean.toString(useMillis));
 		return new CsvSummary(count,  maxValue);
 	}
+	
+	private static String longToString(final long value){
+		// using pre-generated strings reduces memory allocation by up to 25% 
+		
+		if (value < INT_TO_STRING_CACHE_SIZE){
+			return INT_TO_STRING[(int) value];
+		}
+		return String.valueOf(value);
+	}
 }