Update #47 - Singleplayer lag fixes

sources/main/java/com/carrotsearch/hppc/DoubleBufferVisualizer.java

@@ -0,0 +1,33 @@
+package com.carrotsearch.hppc;
+
+/**
+ * Reused buffer visualization routines.
+ *
+ * @see DoubleSet#visualizeKeyDistribution(int)
+ * @see DoubleVTypeMap#visualizeKeyDistribution(int)
+ */
+class DoubleBufferVisualizer {
+  static String visualizeKeyDistribution(double[] buffer, int max, int characters) {
+    final StringBuilder b = new StringBuilder();
+    final char[] chars = ".123456789X".toCharArray();
+    for (int i = 1, start = -1; i <= characters; i++) {
+      int end = (int) ((long) i * max / characters);
+
+      if (start + 1 <= end) {
+        int taken = 0;
+        int slots = 0;
+        for (int slot = start + 1; slot <= end; slot++, slots++) {
+          if (!(Double.doubleToLongBits(buffer[slot]) == 0)) {
+            taken++;
+          }
+        }
+        b.append(chars[Math.min(chars.length - 1, taken * chars.length / slots)]);
+        start = end;
+      }
+    }
+    while (b.length() < characters) {
+      b.append(' ');
+    }
+    return b.toString();
+  }
+}