improve benchmark code

 * path to database can be parametrized
 * do separate warmup and benchmark loops (so JIT can kick in)
 * use fixed random seeds for repeatable runs

sample/Benchmark.java

@@ -11,25 +11,43 @@
 
 public class Benchmark {
 
-    public static void main(String[] args) throws IOException,
-            InvalidDatabaseException {
-        File file = new File("GeoLite2-City.mmdb");
+    private final static int COUNT = 1000000;
+    private final static int WARMUPS = 3;
+    private final static int BENCHMARKS = 5;
+    private final static boolean TRACE = false;
 
-        Reader r = new Reader(file, FileMode.MEMORY_MAPPED);
-        Random random = new Random();
-        int count = 1000000;
+    public static void main(String[] args) throws IOException, InvalidDatabaseException {
+        File file = new File(args.length > 0 ? args[0] : "GeoLite2-City.mmdb");
+        loop("Warming up", file, WARMUPS);
+        loop("Benchmarking", file, BENCHMARKS);
+    }
+
+    private static void loop(String msg, File file, int loops) throws IOException {
+        System.out.println(msg);
+        for (int i = 0; i < loops; i++) {
+            Reader r = new Reader(file, FileMode.MEMORY_MAPPED);
+            bench(r, COUNT, i);
+        }
+        System.out.println();
+    }
+
+    private static void bench(Reader r, int count, int seed) throws IOException {
+        Random random = new Random(seed);
         long startTime = System.nanoTime();
         for (int i = 0; i < count; i++) {
             InetAddress ip = InetAddresses.fromInteger(random.nextInt());
-            if (i % 50000 == 0) {
-                System.out.println(i + " " + ip);
-            }
             JsonNode t = r.get(ip);
+            if (TRACE) {
+                if (i % 50000 == 0) {
+                    System.out.println(i + " " + ip);
+                    System.out.println(t);
+                }
+            }
         }
         long endTime = System.nanoTime();
 
         long duration = endTime - startTime;
-        System.out.println("Requests per second: " + count * 1000000000.0
-                / (duration));
+        long qps = count * 1000000000L / duration;
+        System.out.println("Requests per second: " + qps);
     }
 }