Re: GMP bignum results using double cells.

[Marius Vollmer <mvo@zagadka.de>]

Rob Browning <rlb@defaultvalue.org> writes:

> It looks like the new code is substantially better than 1.7, though if
> I understand correctly, and gc time is included in user time, then it
> appears the improvement was on the gc side, not the computation side.

That looks very good to me.  Certainly good enough to integrate it
into the 1.7 branch.

> Marius, for now, rather than use SCM_CELL_ADDR_1, I mirrored the
> handling of real values like this:
> 
>   #define SCM_I_BIG_MPZ(x) (((scm_t_big_mpz *) SCM2PTR (x))->mpz)
>   #define SCM_BIGP(x) (!SCM_IMP (x) && SCM_TYP16 (x) == scm_tc16_big)
> 
>   typedef struct scm_t_big_mpz
>   {
>     SCM type;
>     mpz_t mpz;
>   } scm_t_big_mpz;
> 
> However, this means that numbers.h now has to include gmp.h, and with
> the SCM_CELL_ADDR_1 approach, it wouldn't.  I'd be happy to arrange
> things whichever way you prefer.

Do we need to define scm_t_big_mpz in numbers.h?  Couldn't it just be
an declared-but-undefined struct there?  Like

  #define SCM_I_BIG_MPZ(x) (((scm_t_big_mpz *) SCM2PTR (x))->mpz)
  #define SCM_BIGP(x) (!SCM_IMP (x) && SCM_TYP16 (x) == scm_tc16_big)

  typedef struct scm_t_big_mpz scm_t_big_mpz;

and later in numbers.c

  struct scm_t_big_mpz
  {
    SCM type;
    mpz_t mpz;
  };

> Also, I was trying to figure out how to add the test for 
> 
>   sizeof (mpz_t) <= 3 * (sizeof (scm_t_bits))
> 
> In order to put it in configure.in, we have to have access to the
> definition of scm_t_bits (or at least SIZEOF_SCM_T_BITS) at configure
> time.  Any thoughts?

We can also put the test somewhere in init.c and have Guile abort
noisily when it fails.

-- 
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