Add exploratory timing harness

timings/src/main/java/com/ankurm/vectorapi/Bench.java

@@ -0,0 +1,41 @@
+package com.ankurm.vectorapi;
+
+import java.util.Arrays;
+
+/**
+ * A deliberately small timing harness. It is NOT a statistical benchmark:
+ * it warms the JIT up, then reports the median and best of several rounds so
+ * that large effects (2x and up) are visible. Use JMH for anything you intend
+ * to defend -- see the jmh/ module in this repository.
+ */
+public final class Bench {
+    public static final int WARMUP_CALLS = 50_000;
+    public static final int ROUND_CALLS  = 5_000;
+    public static final int ROUNDS       = 15;
+
+    public interface Kernel { void run(); }
+
+    /** @return median ns/call over ROUNDS rounds (also prints best). */
+    public static double measure(String label, Kernel k) {
+        for (int i = 0; i < WARMUP_CALLS; i++) k.run();          // force C2 compilation
+        double[] perCall = new double[ROUNDS];
+        for (int r = 0; r < ROUNDS; r++) {
+            long t0 = System.nanoTime();
+            for (int i = 0; i < ROUND_CALLS; i++) k.run();
+            long t1 = System.nanoTime();
+            perCall[r] = (t1 - t0) / (double) ROUND_CALLS;
+        }
+        double[] sorted = perCall.clone();
+        Arrays.sort(sorted);
+        double median = sorted[ROUNDS / 2];
+        double best   = sorted[0];
+        System.out.printf("%-24s median %8.1f ns/call   best %8.1f ns/call%n", label, median, best);
+        return median;
+    }
+
+    public static void speedup(String label, double scalarNs, double vectorNs) {
+        System.out.printf("%-24s %.2fx%n", label, scalarNs / vectorNs);
+    }
+
+    private Bench() {}
+}