Expensive selftests (was: 'hash_map<tree, hash_map<tree, tree>>')

David Edelsohn dje.gcc@gmail.com
Wed Aug 18 13:35:25 GMT 2021


This causes a bootstrap failure for me.

PR/101959

On Tue, Aug 17, 2021 at 5:00 AM Richard Biener via Gcc <gcc@gcc.gnu.org> wrote:
>
> On Tue, Aug 17, 2021 at 8:40 AM Thomas Schwinge <thomas@codesourcery.com> wrote:
> >
> > Hi!
> >
> > On 2021-08-16T14:10:00-0600, Martin Sebor <msebor@gmail.com> wrote:
> > > On 8/16/21 6:44 AM, Thomas Schwinge wrote:
> > >> [...], to document the current behavior, I propose to
> > >> "Add more self-tests for 'hash_map' with Value type with non-trivial
> > >> constructor/destructor", see attached.  OK to push to master branch?
> > >> (Also cherry-pick into release branches, eventually?)
> >
> > (Attached again, for easy reference.)
> >
> > > Adding more tests sounds like an excellent idea.  I'm not sure about
> > > the idea of adding loopy selftests that iterate as many times as in
> > > the patch (looks like 1234 times two?)
> >
> > Correct, and I agree it's a sensible concern, generally.
> >
> > The current 1234 times two iterations is really arbitrary (should
> > document that in the test case), just so that we trigger a few hash table
> > expansions.
>
> You could lower N_init (the default init is just 13!),
> even with just 128 inserted elements you'll trigger
> expansions to 31, 61 and 127 elements.
>
> > For 'selftest-c', we've got originally:
> >
> >     -fself-test: 74775 pass(es) in 0.309299 seconds
> >     -fself-test: 74775 pass(es) in 0.366041 seconds
> >     -fself-test: 74775 pass(es) in 0.356663 seconds
> >     -fself-test: 74775 pass(es) in 0.355009 seconds
> >     -fself-test: 74775 pass(es) in 0.367575 seconds
> >     -fself-test: 74775 pass(es) in 0.320406 seconds
> >
> > ..., and with my changes we've got:
> >
> >     -fself-test: 94519 pass(es) in 0.327755 seconds
> >     -fself-test: 94519 pass(es) in 0.369522 seconds
> >     -fself-test: 94519 pass(es) in 0.355531 seconds
> >     -fself-test: 94519 pass(es) in 0.362179 seconds
> >     -fself-test: 94519 pass(es) in 0.363176 seconds
> >     -fself-test: 94519 pass(es) in 0.318930 seconds
> >
> > So it really seems to be all in the noise?
>
> Yes.  I think the test is OK but it's also reasonable to lower
> the '1234' times and add a comment as to the count should
> trigger hashtable expansions "a few times".
>
> Richard.
>
> > Yet:
> >
> > > Selftests run each time GCC
> > > builds (i.e., even during day to day development).  It seems to me
> > > that it might be better to run such selftests only as part of
> > > the bootstrap process.
> >
> > I'd rather have thought about a '--param self-test-expensive' (or
> > similar), and then invoke the selftests via a new
> > 'gcc/testsuite/selftests/expensive.exp' (or similar).
> >
> > Or, adapt 'gcc/testsuite/gcc.dg/plugin/expensive_selftests_plugin.c',
> > that is, invoke them via the GCC plugin mechanism, which also seems to be
> > easy enough?
> >
> > I don't have a strong opinion about where/when these tests get run, so
> > will happily take any suggestions.
> >
> >
> > Grüße
> >  Thomas
> >
> >
> > -----------------
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