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

[David Blaikie via llvm-commits]

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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