multitime: a better time utility

Unix's time utility is a simple and often effective way of measuring how long a command takes to run. Unfortunately, running a command once can give misleading timings: the process may create a cache on its first execution, running faster subsequently; other processes may cause the command to be starved of CPU or IO time; etc. It is common to see people run time several times and take whichever values they feel most comfortable with. Inevitably, this causes problems.

multitime is, in essence, a simple extension to time which runs a command multiple times and prints the timing means (with confidence intervals), standard deviations, minimums, medians, and maximums having done so. This can give a much better understanding of the command's performance.

Why should you use multitime?

If you want to do any of the following, then multitime is worth considering:

• You want to run a command several times to understand how its timings naturally vary.
• You want to run a command several times so that temporary blips in system activity do not distort the timings.
• You need different executions of a command being timed to have different inputs / outputs.
• You want to compare the timing of multiple commands (e.g. for benchmarking purposes).

multitime can also be used as a drop-in replacement for the POSiX time command: when invoked as time (e.g. via a symlink), multitime behaves as time. For most users, therefore, multitime can safely replace the time binary, even if you don't make use of its advanced features.

Example usage

The example below shows a simple benchmark of an awk program. In this case the program has been executed 5 times (-n 5).

$ multitime -n 5 awk "function fib(n) \
>   { return n <= 1 ? 1 : fib(n - 1) + fib(n - 2) } BEGIN { fib(30) }"
===> multitime results
1: awk "function fib(n)   { return n <= 1 ? 1 : fib(n - 1) + fib(n - 2) } BEGIN { fib(30) }"
            Mean                Std.Dev.    Min         Median      Max
real        1.860+/-0.0013      0.021       1.837       1.856       1.895
user        1.833+/-0.0005      0.013       1.812       1.836       1.846
sys         0.002+/-0.0000      0.003       0.000       0.000       0.008

Installing

Formal released of multitime can be downloaded here: http://tratt.net/laurie/src/multitime/releases.html.

Formal releases can be built and installed with:

$ ./configure
$ make install

The latest source can be cloned with:

$ git clone git://github.com/ltratt/multitime.git

and built with:

make -f Makefile.bootstrap
$ ./configure
$ make install

Want to know more?

More details can be found at the http://tratt.net/laurie/src/multitime/