multitime: a better time utility
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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?
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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
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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
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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?
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More details can be found at the http://tratt.net/laurie/src/multitime/
