validation and profiles

lib/statistics/cma/Cma.md

@@ -61,6 +61,20 @@ $$ M_n = \frac{1}{n} \sum_{i=1}^{n} x_i = \frac{(n-1) \cdot M_{n-1} + x_n}{n} $$
 
 ## Performance Profile
 
+### Operation Count (Streaming Mode)
+
+Cumulative Mean Arithmetic uses a simple running sum divided by count — no window, no buffer.
+
+| Operation | Count | Cost (cycles) | Subtotal |
+| :--- | :---: | :---: | :---: |
+| Add value to running sum | 1 | 1 cy | ~1 cy |
+| Increment count | 1 | 1 cy | ~1 cy |
+| Divide sum by count | 1 | 4 cy | ~4 cy |
+| NaN guard + state update | 1 | 2 cy | ~2 cy |
+| **Total** | **O(1)** | — | **~8 cy** |
+
+Cheapest mean variant — no buffer, no window management. Throughput limited by division latency (~4 cy on modern x86).
+
 | Metric | Score | Notes |
 | :--- | :--- | :--- |
 | **Throughput** | ~5 ns/bar | Single division per update. |