test: expose error bars and the extra stats test keeps track of

[erickt]

There are a bunch stats that libtest keeps track of that we don't expose. This adds --error-bar and --stats to expose this to the users.

[huonw]

Cool! Could you give the output of an example using these?

[erickt]

@huonw: Sure!

error bars:

test bench_buf_writer_1                             ... bench: 20000 |  [-----******#*****-----]           | 40000:     27104 ns/iter (+/- 11669)
test bench_buf_writer_1_inline_always               ... bench: 10000 |           [---*****#****--]         | 40000:     25797 ns/iter (+/- 11614)
test bench_buf_writer_1_inline_never                ... bench: 10000 |            [-------*****#***---]    | 40000:     29315 ns/iter (+/- 15064)
test bench_buf_writer_2                             ... bench: 10000 |          [---******#***---]         | 40000:     25772 ns/iter (+/- 12184)
test bench_buf_writer_2_inline_always               ... bench: 10000 |          [--******#****---]         | 40000:     24473 ns/iter (+/- 12945)
test bench_buf_writer_2_inline_never                ... bench: 20000 | [---******#*********-----]          | 40000:     25447 ns/iter (+/- 12935)

stats:

test bench_buf_writer_1                             ... bench: (min=21284.15, q1=25706.75, med=29158, q3=31405.5, max=34307.4)
test bench_buf_writer_1_inline_always               ... bench: (min=18733.7, q1=21098.25, med=25244.5, q3=29939, max=31266.8)
test bench_buf_writer_1_inline_never                ... bench: (min=21073.95, q1=23568.25, med=26339.5, q3=30946.25, max=33214.35)
test bench_buf_writer_2                             ... bench: (min=18662.95, q1=20094.75, med=24551, q3=28035.25, max=29277.05)
test bench_buf_writer_2_inline_always               ... bench: (min=17437.55, q1=18603.25, med=21153, q3=25530.5, max=29809.7)
test bench_buf_writer_2_inline_never                ... bench: (min=20313, q1=28757.75, med=30551, q3=33171.5, max=34707.1)
test bench_buf_writer_3                             ... bench: (min=22250.7, q1=29062.25, med=34385, q3=36875, max=39247.7)

[emberian]

Ohhh, fancy!