adding ema

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/util/ema.h

@@ -0,0 +1,44 @@
+/*++
+Copyright (c) 2018 Microsoft Corporation
+
+Module Name:
+
+    ema.h
+
+Abstract:
+
+    Exponential moving average in the style of CaDiCal.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2018-05-03
+
+Revision History:
+
+--*/
+#ifndef EMA_H_
+#define EMA_H_
+
+class ema {
+    double m_alpha, m_beta, m_value;
+    unsigned m_period, m_wait;
+
+ public:
+    ema() { memset(this, 0, sizeof(*this)); }
+
+    ema(double alpha): 
+        m_alpha(alpha), m_beta(1), m_value(0), 
+        m_period(0), m_wait(0) {}
+
+    double operator() const { return m_value; }
+
+    void update(double x) {
+        m_value += m_beta * (x - m_value);
+        if (m_beta <= m_alpha || m_wait--) return;
+        m_wait = m_period = 2*(m_period + 1) - 1;
+        m_beta *= 0.5;
+        if (m_beta < m_alpha) m_beta = m_alpha;        
+    }
+};
+
+#endif

src/util/sorting_network.h

@@ -371,6 +371,9 @@ Notes:
                 break;
             case ordered_at_most_1:
                 return mk_ordered_exactly_1(full, n, xs);
+            default:
+                UNREACHABLE();
+                return mk_ordered_exactly_1(full, n, xs);                
             }
 
             if (full) {