TimeElapsed

The C++11 header file to provide a simple TIME_ELAPSED macros to measure the elapsed time of a code block.

The code has been tested with VisualStudio 2013 on Windows7 and g++ 4.8.2 on CentOS7.

1. Header file

TimeElapsed.hpp

2. Macro API

2.1. TIME_ELAPSED(target_code)

Measure the elapsed time of target_code and printout the time after executing it. target_code can be a whole code block as well as a simple expression.

The output line is formated as:

ElapsedTime: <file_name> at L.<line_number>     cnt:<iteration_count>    <elapsed_time> msec

For example,

ElapsedTime: main.c at L.25                     cnt:1           25.400 msec

2.2. TIME_ELAPSED_EXP(target_code)

This macro is the same as TIME_ELAPSED() except that the header is the stringified target_code. For example,

ElapsedTime: f += very_slow_func(123);          cnt:1           25.400 msec

2.3. TIME_ELAPSED_MARKER(marker,body)

This macro is the same as TIME_ELAPSED() except that the header is given by the user. For example,

ElapsedTime: Arigorithm 1  param x=4,y=7        cnt:1           11.200 msec

2.4. Loop versions

The following macros will measure the elapsed time after running a loop of target_code by n times.

• TIME_ELAPSED_N(n,body)
• TIME_ELAPSED_EXP_N(n,body)
• TIME_ELAPSED_MARKER_N(n,marker,body)

The elapsed time is calculated for the whole loop run.

2.5. NO_TIME_ELAPSED_MEASUREMENT

If defined, TIME_ELAPSED* macros will not measure the time nor generate any output.

3. Tutorial

Basically you can measure the elapsed time of the concerned code block by inserting TIME_ELAPSED macro around.

For example, the following code block can be measured

	double target = atan(1.0);

	// Leibniz formula: qpi->PI/4
	long long int d = 1;
	double qpi = 1.0;
	do {
		d += 2; qpi -= 1.0 / d;
		d += 2; qpi += 1.0 / d;
	} while (qpi-target > EPSILON);
	
	std::cout << 4.0*qpi << std::endl;

like this:

	double target = atan(1.0);

TIME_ELAPSED(
	// Leibniz formula: qpi->PI/4
	long long int d = 1;
	double qpi = 1.0;
	do {
		d += 2; qpi -= 1.0 / d;
		d += 2; qpi += 1.0 / d;
	} while (qpi-target > EPSILON);
);

	std::cout << 4.0*qpi << std::endl;

After the completion of do{...}while, TIME_ELAPSED will print the elapsed time.

You can see more examples in main.cpp.

4. Porability

The header file uses C++11 standard only: macro, lambda, chrono, string, and ostream. The code should be portable to any OS.

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