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Re: Automake::Conditional::simplify (Quine-McCluskey)

From: Raja R Harinath
Subject: Re: Automake::Conditional::simplify (Quine-McCluskey)
Date: Sun, 17 Nov 2002 10:13:14 -0600
User-agent: Gnus/5.090008 (Oort Gnus v0.08) Emacs/21.3.50 (i686-pc-linux-gnu)


Alexandre Duret-Lutz <address@hidden> writes:

>>>> "Raja" == Raja R Harinath <address@hidden> writes:
> [...]
>  Raja> $variable_conditions($var)
>  Raja> -> sub_conditions($cond)
>  Raja> -> invert
>  Raja> -> simplify
>  Raja> -> mult_cond($cond)
>  Raja> Almost self-documenting :-)
> Sounds great.  (It's what you suggested months ago, right?)

Yep.  But, it is cleaner to express now, with things out of line.

>  Raja> We can revisit this later, I guess.  But, we may have to
>  Raja> put in a warning in here if $rank >
>  Raja> significant_bits_in_float.
> BTW, I wonder if it's even possible to use so much conditionals
> in Automake.  

Exactly.  I don't think it's worth it.  Nesting 25 conditionals in would be a nightmare.

> Calling A::CS::permutations with 25 conditionals seems somewhat
> memory-consuming.  (Maybe it could help -- not in worst cases -- to
> always call A::CS::simplify before A::CS::invert)

And, you could switch to a more compact representation for
A::Conditional: move %var_rank and @rank_var from A::CS::simplify
into A::Conditional, and represent conditionals directly as bitsets.

A::C::permutations (somewhat of a misnomer) is after
all just counting from 00..0000 to 11..1111 for as many bits as there
are conditionals.  So, 25 conditionals means 2^25 "permutations".

If you really want to worry about scalability, A::CS::invert would be
better written as a product-of-sums to sum-of-products converter,
rather than explicitly enumerating every truth-value candidate.

> 2002-11-17  Alexandre Duret-Lutz  <address@hidden>
>       * lib/Automake/ (simplify): New method.
>       (string): Call string for each Conditional.
>       * (variable_not_always_defined_in_cond): Return
>       a simplified ConditionalSet.
>       (macro_define, require_variables): Adjust.
>       * tests/ (TEST): Add library3.test.
>       * tests/library3.test: New file.
>       * tests/pluseq9.test: Adjust.

Looks good.

- Hari
Raja R Harinath ------------------------------ address@hidden

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