[m-rev.] for prelim review: fix compiler performance problems on large programs

[Julien Fischer]

On Tue, 28 Mar 2006, Zoltan Somogyi wrote:

> On 28-Mar-2006, Julien Fischer <juliensf at cs.mu.OZ.AU> wrote:
> > > My laptop still tries to swap itself to death on the full version of
> > > training_cars.m (it has only 512 Mb), but the compiler now works fine
> > > on a version containing about 20% of its clauses, whereas previously
> > > it couldn't compile it at all.
> >
> > That should be added as a test case, but whether it it is run will need to be
> > controlled by an environment variable, e.g. ENABLE_BIG_TEST_CASES or
> > something.  Since, it's causing your laptop to thrash, I'd hate to think about
> > what it might do to mine.
>
> I am not sure about the usefulness of a test case that fails by killing the
> machine. Remember, the symptom is the usage of lots of virtual memory.
> On Linux, if the machine runs out of swap space, it will cause the next
> call to malloc to fail, even if the malloc is by a process other than
> the one that used up all the memory.

I didn't necessarily mean using the full version as a test case, even the
version that contains 20% of the clauses would suffice (assuming there is
a mechanism that limits it to machines that have sufficient memory.)

> > >  :- pred transform_goal(goal::in, prog_substitution::in, hlds_goal::out,
> > > -    prog_varset::in, prog_varset::out,
> > > +    int::out, prog_varset::in, prog_varset::out,
> > >      module_info::in, module_info::out, qual_info::in, qual_info::out,
> > >      svar_info::in, svar_info::out, io::di, io::uo) is det.
> >
> > Would it be possible to use an equivalence type for the int argument
> > here (and below)?
>
> What equivalence type name would be clearer to you?

number_of_clauses or num_clauses (basically something that gives me some
idea of what that argument is supposed to be doing.)

Julien.
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