Benchmarking code that mutates its input data

[Orson Cart]

We have a slice containing a mix of data items, some of which are deemed to be 'valid', some 'invalid'. We need to remove the invalid items.

In the current implementation we have a function which takes the slice as input and removes the invalid' elements from it in place i.e. not from a copy.  So, after the function has completed, the slice will no longer contain any of the invalid elements.

We have alternative approaches to doing this but ideally we'd like to benchmark each. However we're struggling to set up the test data for this one because after the first call there will be no data to change - if the profiler were to call the function 1000 times, only the first call will have done any actual work. To make the benchmarked function do the same work each time we'd have to set up fresh data for each call to the function. We can do that but we don't want that setup to show in the timing for the benchmark.

Does anyone know of a solution to this?

TIA,

Orson

[Sam Whited]

I'd like to quickly suggest that the "filtering without allocating"
technique from this page is probably what you want and you may want to
consider if/why you even need to benchmark this:
https://github.com/golang/go/wiki/SliceTricks

However, if you do need to benchmark it:

On Wed, Mar 18, 2020, at 11:46, Orson Cart wrote:
> - if the profiler were to call the function 1000 times, only the first
> call will have done any actual work. To make the benchmarked function
> do the same work each time we'd have to set up fresh data for each
> call to the function. We can do that but we don't want that setup to
> show in the timing for the benchmark.
>
> Does anyone know of a solution to this?

Just call b.ResetTimer() after setting up your data: https://godoc.org/testing#B.ResetTimer

—Sam

--
Sam Whited

[Robert Engels]

The test package has methods to disable the timing - wrap the setup in these.

> On Mar 18, 2020, at 10:50 AM, Sam Whited <s...@samwhited.com> wrote:
>
> I'd like to quickly suggest that the "filtering without allocating"

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[Orson Cart]

On Wednesday, 18 March 2020 17:53:05 UTC, Robert Engels wrote:

The test package has methods to disable the timing - wrap the setup in these.

Thanks. I guess you're referring to StoptTimer, StartTimer and ResetTimer?

I think that in my case ResetTimer will do the trick. Unless I'm mistaken StartTimer and StopTimer are useful in more complex scenarios.

[Orson Cart]

On Wednesday, 18 March 2020 15:50:33 UTC, Sam Whited wrote:

Just call b.ResetTimer() after setting up your data: https://godoc.org/testing#B.ResetTimer

Thanks, I'll take a look