sheet 5

Sheet_5/bsp_5_1/timing.h

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+#pragma once
+#include <chrono>                  // timing
+#include <stack>
+
+using Clock = std::chrono::system_clock;   //!< The wall clock timer chosen
+//using Clock = std::chrono::high_resolution_clock;
+using TPoint= std::chrono::time_point<Clock>;
+
+// [Galowicz, C++17 STL Cookbook, p. 29]
+inline 
+std::stack<TPoint> MyStopWatch; //!< starting time of stopwatch
+
+/** Starts stopwatch timer.
+ *  Use as @code tic(); myfunction(...) ; double tsec = toc();  @endcode
+ * 
+ *  The timining is allowed to be nested and the recent time is stored on top of the stack.
+ * 
+ *  @return recent time
+ *  @see toc
+ */
+inline auto tic()
+{
+    MyStopWatch.push(Clock::now());
+    return MyStopWatch.top();
+}
+ 
+/** Returns the elapsed time from stopwatch. 
+ * 
+ * The time from top of the stack is used
+ * if time point @p t_b is not passed as input parameter.
+ * Use as @code tic(); myfunction(...) ; double tsec = toc();  @endcode
+ * or as @code auto t_b = tic(); myfunction(...) ; double tsec = toc(t_b);  @endcode
+ * The last option is to be used in the case of 
+ * non-nested but overlapping time measurements.
+ * 
+ * @param[in]  t_b start time of some stop watch
+ * @return elapsed time in seconds.
+ *
+*/ 
+inline double toc(TPoint const &t_b = MyStopWatch.top())
+{
+    // https://en.cppreference.com/w/cpp/chrono/treat_as_floating_point
+    using Unit      = std::chrono::seconds;
+    using FpSeconds = std::chrono::duration<double, Unit::period>;        
+    auto t_e = Clock::now();
+    MyStopWatch.pop();
+    return FpSeconds(t_e-t_b).count();
+}
+
+#include <iostream>
+#include <string>
+/** Executes function @p f and measures/prints elapsed wall clock time in seconds
+ * 
+ * Call as
+ * @code measure("Time for (b = b + 1)", [&]() {
+        thrust::transform(b.begin(), b.end(), b.begin(), increment());
+    }); @endcode
+ * 
+ * @param[in]  label  additional string to be printed with the measurement.
+ * @param[in]  f      function to execute.
+ * @author Therese Bösmüller, 2025
+ *
+*/ 
+auto measure = [](const std::string& label, auto&& f) {
+        auto start    = std::chrono::high_resolution_clock::now();
+        f();
+        auto stop     = std::chrono::high_resolution_clock::now();
+        auto duration = std::chrono::duration_cast<std::chrono::microseconds>(stop - start).count();
+        std::cout << label << ": " << duration << " microseconds" << std::endl;
+};          // ';' is needed for a visible documentation of this lambda-function