We don't always have precise integers with which to store, so allow
degrading to double precision floating point based on available input.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
https://en.wikipedia.org/wiki/Trimean
The trimean is a the most efficient 3-point L-estimator (estimator
of central tendency, i.e. average), even more robust than the
median at estimating the average of a sample population.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
https://en.wikipedia.org/wiki/Interquartile_mean
The IQM is a truncated mean and so is very similar to the scoring
method used in sports that are evaluated by a panel of judges:
discard the lowest and the highest scores; calculate the mean
value of the remaining scores.
It's useful to hide outliers in measurements (due to cold cache etc),
without having to worry too much about the actual distribution.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Chris mentioned he wanted to be able to measure a variable "for one
second" and use igt_stats to store them. That's one case where we don't
know the number of data points upfront.
We should really support that, so here it is.
v2: Just free ->sorted when a new capacity is needed.
ensure_sorted_values() will then reallocate the array to the new
capacity on demand (Chris)
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
This changes how we compute the variance. We want an unbiased variance
when reasoning about a sample.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Because the structure started small, I initialized every member
directly, but that means that the new fields added weren't properly
initialized (sigh!). Zero the whole thing first then.
Also, the punishment for introducing a bug should be to write the
corresponding unit test. It's not a perfect one, but I'll take it.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
The master plan would be to get a bit more stats in it, at least the
standard deviation and confidence interval. Just need the average for
now.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
