[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Automake::Conditional::simplify (Quine-McCluskey)
From: |
Raja R Harinath |
Subject: |
Re: Automake::Conditional::simplify (Quine-McCluskey) |
Date: |
Sat, 16 Nov 2002 18:41:52 -0600 |
User-agent: |
Gnus/5.090008 (Oort Gnus v0.08) Emacs/21.3.50 (i686-pc-linux-gnu) |
Hi,
Alexandre Duret-Lutz <address@hidden> writes:
>>>> "Raja" == Raja R Harinath <address@hidden> writes:
>
> Raja> And, dare I say, implement Quine-McCluskey minimization ;-)
>
> You've just won another patch to review :)
Man, that was quick :-)
[snip]
> Index: automake.in
> ===================================================================
> RCS file: /cvs/automake/automake/automake.in,v
> retrieving revision 1.1388
> diff -u -r1.1388 automake.in
> --- automake.in 14 Nov 2002 22:37:29 -0000 1.1388
> +++ automake.in 16 Nov 2002 12:31:04 -0000
> @@ -6184,7 +6184,7 @@
> push @res, $icond
> if ($cond->true_when ($icond)); # (3)
> }
> - return @res;
> + return (new Automake::ConditionalSet @res)->simplify;
> }
This is for later cleanup... But, it would be nice if more of the
functionality of variable_not_always_defined_in_cond() is moved into
Automake::Conditional[Set].
If A::CS had two methods 'sub_conditions':
new A::CS("A_FALSE B_TRUE", "A_TRUE C_TRUE", "A_TRUE D_FALSE")
->sub_conditions("A_TRUE")
== new A::CS("C_TRUE", "D_FALSE")
and 'mult_cond':
new A::CS("C_TRUE D_FALSE", "E_FALSE")->mult_cond("F_TRUE G_FALSE")
== new A::CS("C_TRUE D_FALSE F_TRUE G_FALSE", "E_FALSE F_TRUE G_FALSE")
Then v_n_a_d_i_c($var, $cond) would be
$variable_conditions($var)
->sub_conditions($cond)
->invert
->simplify
->mult_cond($cond)
Almost self-documenting :-)
[snip]
> Index: lib/Automake/ConditionalSet.pm
> ===================================================================
[snip]
> +sub simplify ($) # Based on Quime-McCluskey's algorithm.
That should be 'Quine'.
> + # Fire the relevant bit in the strings.
> + if ($2 eq 'FALSE')
> + {
> + $false |= 1 << $rank;
> + }
> + else
> + {
> + $true |= 1 << $rank;
> + }
> + }
This means that you're limited to ~25 conditionals, or you need
use Math::BigInt;
on top, or use a custom bitset. We can revisit this later, I guess.
But, we may have to put in a warning in here if $rank >
significant_bits_in_float.
> + # Real work. Let's combine terms.
> +
> + # Process terms in diminishing size order. Those
> + # involving the maximum number of variables first.
> + for (my $m = $#subcubes; $m > 0; --$m)
> + {
> + my $m_subcubes = $#{$subcubes[$m]};
> + # Consider all terms with $m variables.
> + for (my $j = 0; $j <= $m_subcubes; ++$j)
> + {
> + my $tj = $subcubes[$m][$j];
> + next unless $tj; # Skip deleted terms.
Given your loop below, how can $tj be deleted?
> + my $jtrue = $tj->[0];
> + my $jfalse = $tj->[1];
> +
> + # Compare them with all other terms with $m variables.
> + COMBINATION:
> + for (my $k = $j + 1; $k <= $m_subcubes; ++$k)
> + {
> + my $tk = $subcubes[$m][$k];
> + next COMBINATION unless $tk; # Skip deleted terms.
Likewise with $tk.
> + # Filter-out implied terms.
[snip]
(BTW, is almost equivalent to Automake::Conditional::reduce).
> + next if $tj->[2]; # Skip covered terms. (If $tj covers some
> + # terms, they will be filtered out when
> + # we later process the term that covers $tj.)
See below:
> + for (my $n = $m + 1; $n <= $#subcubes; ++$n)
> + {
> + my $n_subcubes = $#{$subcubes[$n]};
> +
> + for (my $k = 0; $k <= $n_subcubes; ++$k)
> + {
> + my $tk = $subcubes[$n][$k];
> + next if $tk->[2]; # Skip covered terms.
Don't you need a
next unless $tk;
> + my $ktrue = $tk->[0];
> + my $kfalse = $tk->[1];
> +
> + next unless $ktrue == ($ktrue | $jtrue);
> + next unless $kfalse == ($kfalse | $jfalse);
> +
> + delete $subcubes[$n][$k];
> + }
> + }
> + }
Might as well delete all covered $tj here. You're going to skip over
them all the time, anyway.
> + }
Actually, this whole part can be pulled out, and done in a separate
(nested-)loop, a la stage 2 of QM. You can even do somewhat less work
if $m ranges from 1 upwards rather than downwards to 1, and this can
even be combined with the next loop that collects the or_conds.
- Hari
--
Raja R Harinath ------------------------------ address@hidden
- Automake::Conditional::simplify (Quine-McCluskey), Alexandre Duret-Lutz, 2002/11/16
- Re: Automake::Conditional::simplify (Quine-McCluskey),
Raja R Harinath <=
- Re: Automake::Conditional::simplify (Quine-McCluskey), Alexandre Duret-Lutz, 2002/11/17
- Re: Automake::Conditional::simplify (Quine-McCluskey), Raja R Harinath, 2002/11/17
- Re: Automake::Conditional::simplify (Quine-McCluskey), Alexandre Duret-Lutz, 2002/11/18
- Re: Automake::Conditional::simplify (Quine-McCluskey), Raja R Harinath, 2002/11/18
- Re: Automake::Conditional::simplify (Quine-McCluskey), Alexandre Duret-Lutz, 2002/11/19
- Automake::Conditional::invert, Alexandre Duret-Lutz, 2002/11/19
- Re: Automake::Conditional::invert, Raja R Harinath, 2002/11/19
- Re: Automake::Conditional::invert, Alexandre Duret-Lutz, 2002/11/20
- Re: Automake::Conditional::invert, Raja R Harinath, 2002/11/20
- Re: Automake::Conditional::invert, Alexandre Duret-Lutz, 2002/11/20