Added a tool for timing blocks of code

dlib/timing.h

+// Copyright (C) 2011  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_TImING_H__
+#define DLIB_TImING_H__
+
+#include "dlib/misc_api.h"
+
+#include <iostream>
+
+/*!A timing
+
+    This set of functions is useful for determining how much time is spent
+    executing blocks of code.  Consider the following example:
+
+    int main()
+    {
+        using namespace dlib::timing;
+        for (int i = 0; i < 10; ++i)
+        {
+            // timing block #1
+            start(1);
+            dlib::sleep(500);
+            stop(1);
+
+            // timing block #2
+            start(2);
+            dlib::sleep(1000);
+            stop(2);
+        }
+
+        print();
+    }
+
+    This program would output:
+        Timing report: 
+            1: 5.0 seconds
+            2: 10.0 seconds
+
+    So we spent 5 seconds in block #1 and 10 seconds in block #2
+!*/
+
+namespace dlib
+{
+    namespace timing
+    {
+        const int TIME_SLOTS = 500;
+
+        inline uint64* time_buf()
+        {
+            static uint64 buf[TIME_SLOTS] = {0};
+            return buf;
+        }
+
+        inline timestamper& ts()
+        {
+            static timestamper ts_;
+            return ts_;
+        }
+
+        inline void start(int i )
+        {
+            time_buf()[i] -= ts().get_timestamp();
+        }
+
+        inline void stop(int i)
+        {
+            time_buf()[i] += ts().get_timestamp();
+        }
+
+        inline void print()
+        {
+            using namespace std;
+            cout << "Timing report: " << endl;
+            for (int i = 0; i < TIME_SLOTS; ++i)
+            {
+                if (time_buf()[i] != 0)
+                {
+                    double time = time_buf()[i]/1000.0;
+                    if (time < 1000)
+                        cout << "  " << i << ": " << time << " milliseconds" << endl;
+                    else if (time < 1000*1000)
+                        cout << "  " << i << ": " << time/1000.0 << " seconds" << endl;
+                    else if (time < 1000*1000*60)
+                        cout << "  " << i << ": " << time/1000.0/60.0 << " minutes" << endl;
+                    else
+                        cout << "  " << i << ": " << time/1000.0/60.0/60.0 << " hours" << endl;
+                }
+            }
+        }
+    }
+}
+
+
+#endif // DLIB_TImING_H__
+