mxs-1777: maxutils additions

Adding classes for calculating averages. Update StopWatch to C++11.

maxutils/maxbase/include/maxbase/average.hh

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2018 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+#pragma once
+
+#include <maxbase/ccdefs.hh>
+
+#include <vector>
+
+namespace maxbase
+{
+/** Regular average, but calculated cumulatively. */
+class CumulativeAverage
+{
+public:
+    // add an average made of num_samples
+    void   add(double ave, int num_samples = 1);
+    double average() const;
+    int    num_samples() const;
+    void   reset();
+    CumulativeAverage& operator+=(const CumulativeAverage& rhs);
+    CumulativeAverage operator+(const CumulativeAverage& rhs) const;
+private:
+    double m_ave = 0;
+    int    m_num_samples = 0;
+    int    m_num_last_added = 0;
+};
+
+/** Exponential Moving Average. */
+class EMAverage
+{
+public:
+    EMAverage(double min_alpha, double max_alpha, int sample_max);
+
+    /* add an average made of num_samples
+    *  alpha = m_min_alpha + m_max_alpha * std::min(double(num_samples) / sample_max, 1.0);
+    *  ave = alpha * ave + (1 - alpha) * sample; */
+    void   add(double ave, int num_samples = 1);
+    void   add(const CumulativeAverage& ca);
+    double average() const;
+    int    num_samples() const;
+    void   set_sample_max(int sample_max);
+    int    sample_max() const;
+    void   reset();
+private:
+    const double  m_min_alpha;
+    const double  m_max_alpha;
+    int     m_sample_max;
+    int     m_num_samples = 0;
+    double  m_ave = 0;
+};
+
+} // maxbase

maxutils/maxbase/include/maxbase/stopwatch.hh

@@ -20,18 +20,22 @@
 namespace maxbase
 {
 
-#if __cplusplus >= 201103
-typedef std::chrono::steady_clock Clock;
-#else
-typedef std::chrono::system_clock Clock;
-#endif
+using Clock = std::chrono::steady_clock;
 
 struct Duration : public Clock::duration // for ADL
 {
-    // gcc 4.4 does not inherit constructors, so this is a bit limited.
+    using Clock::duration::duration;
     Duration() = default;
-    Duration(long long l) : Clock::duration(l) {}
     Duration(Clock::duration d) : Clock::duration(d) {}
+    Duration(long long l) : Clock::duration(l) {} // FIXME. Get rid of this.
+
+    explicit Duration(double secs) : Duration{rep(secs * period::den / period::num)}
+    {}
+
+    double secs()
+    {
+        return std::chrono::duration<double>(*this).count();
+    }
 };
 
 typedef std::chrono::time_point<Clock, Duration> TimePoint;