[PATCH] D16726: [Profiling] Speed up unittests by ~5x

[David Blaikie via llvm-commits]

On Mon, Feb 8, 2016 at 4:00 PM, Xinliang David Li <davidxl at google.com>
wrote:

> Yes, if we talk about all tests in different repos collectively, 0 is
> probably covered -- but that is still an assumption from the
> unittest's point of view.
>

Ah, sure - I agree it (along with any other API surface area) should be
covered by a unit test, even if the codepath is also covered by a higher
level test of some kind.

But it looks like the 0 padding case is covered by other /unit/ tests in
the same file. This seems like a reasonable case of test case reduction by
combination (if you have {a, b} x {x, y} to test you can test it in two
cases {a, x}, {b, y} rather than running 4 tests, since the features are
independent).


>
> David
>
> On Mon, Feb 8, 2016 at 3:55 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> > On Mon, Feb 8, 2016 at 3:53 PM, Xinliang David Li <davidxl at google.com>
> > wrote:
> >>
> >> On Mon, Feb 8, 2016 at 3:30 PM, David Blaikie <dblaikie at gmail.com>
> wrote:
> >> >
> >> >
> >> > On Mon, Feb 8, 2016 at 3:17 PM, Xinliang David Li <davidxl at google.com
> >
> >> > wrote:
> >> >>
> >> >> On Mon, Feb 8, 2016 at 3:12 PM, David Blaikie <dblaikie at gmail.com>
> >> >> wrote:
> >> >> >
> >> >> >
> >> >> > On Mon, Feb 8, 2016 at 3:08 PM, Xinliang David Li
> >> >> > <davidxl at google.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> On Mon, Feb 1, 2016 at 10:44 AM, David Blaikie <
> dblaikie at gmail.com>
> >> >> >> wrote:
> >> >> >> >
> >> >> >> >
> >> >> >> > On Fri, Jan 29, 2016 at 5:58 PM, Xinliang David Li
> >> >> >> > <davidxl at google.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> To clarify, it is not 128 iterations, but creating a symbol
> table
> >> >> >> >> with
> >> >> >> >> 128 entries -- which is a reasonable size.
> >> >> >> >
> >> >> >> >
> >> >> >> > We don't generally test on "realistic" sized inputs in the
> >> >> >> > regression
> >> >> >> > suite.
> >> >> >> > We write targeted tests for functionality. Broad testing is done
> >> >> >> > in
> >> >> >> > the
> >> >> >> > test-suite and other integration level testing.
> >> >> >> >
> >> >> >> >>
> >> >> >> >> Test coverage wise, it is probably the same as a 3-entry
> symtab.
> >> >> >> >
> >> >> >> >
> >> >> >> > Then let's use a 3-entry symtab.
> >> >> >> >
> >> >> >> > (why 3? Because it tests the boundaries (first and last) and one
> >> >> >> > "normal"
> >> >> >> > case of a non-boundary value - while the boundaries probably
> >> >> >> > aren't
> >> >> >> > interesting in this algorithm, it's cheap enough to just follow
> >> >> >> > that
> >> >> >> > common
> >> >> >> > practice in test case design)
> >> >> >>
> >> >> >> Will update it to 3.
> >> >> >>
> >> >> >> >
> >> >> >> > I'm also curious about the padding parameter - what does it do?
> >> >> >> > Choose
> >> >> >> > how
> >> >> >> > many null characters go between each value? What effect does
> that
> >> >> >> > have/why
> >> >> >> > is that a tuning parameter? (understanding what it's for can
> help
> >> >> >> > us
> >> >> >> > choose
> >> >> >> > appropriate test cases/coverage for that functionality)
> >> >> >>
> >> >> >> Internal padding bytes (for alignment to 4 bytes) can be zero to
> 3.
> >> >> >
> >> >> >
> >> >> > Any idea what's particularly useful to test here? (does it just
> >> >> > assert
> >> >> > that
> >> >> > the parameter is [0,3] ? Or does it have well defined behavior
> >> >> > (returning an
> >> >> > error code? doing something else?) outside that range? is any case
> >> >> > more
> >> >> > interesting than any other - or just a simple loop for [0,Padding]
> >> >> > done
> >> >> > at
> >> >> > some point in the algorithm? Does anything test that the algorithm
> >> >> > emitted
> >> >> > the right padding?)
> >> >>
> >> >> It tests that the reader is (flexible) and capable of handing padding
> >> >> bytes not produced by the writer.  How many paddings should be
> emitted
> >> >> is not specified. For instance, if some producer forces 8 byte
> >> >> alignment, it should be handled too.
> >> >
> >> >
> >> > Ah, OK - perhaps we could just test one pseudo-random (if it's really
> >> > just a
> >> > "while (null byte)" loop to ignore the padding - I'd probably pick 2
> >> > bytes
> >> > of padding, but don't mind any small number) amount of padding to test
> >> > that
> >> > the reader ignores it, rather than testing several amounts of padding?
> >> > Alternatively/in addition, might be good to test these features
> >> > separately
> >> > to make triage easier? Rather than combining compression and padding
> >> > together - unless there's an interesting interaction between the two
> >> > features in the implementation?
> >> >
> >>
> >> I think 0 is more special here, so I would pick 0 and 1 byte.
> >
> >
> > Is zero bytes of padding not already covered by any other tests? (I
> assume
> > it's covered by most tests as it sounds like it's the common case?)
> >
> >>
> >> > You say "padding bytes not produced by the writer" - does the writer
> >> > produce
> >> > zero bytes of padding, or some amount of padding that's just not the
> >> > same
> >> > amounts as are being tested here?
> >>
> >> The writer can produce 0 or more padding bytes, the assembler and
> >> linker may or may not pad more. The purpose of the testing is that the
> >> reader does not depend/care about those behavior.
> >>
> >> David
> >>
> >> >
> >> > - David
> >
> >
>
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