[Python-checkins] Who are the decimal volunteers? Re: cpython: Resize the coefficient to MPD_MINALLOC also if the requested size is below

[Jim Jewett]

I remember that one of the concerns with cdecimal was whether it could
be maintained by anyone except Stefan (and a few people who were
already overcommitted).

If anyone (including absolute newbies) wants to step up, now would be
a good time to get involved.

A few starter questions, whose answer it would be good to document:

Why is there any need for MPD_MINALLOC at all for (immutable) numbers?

I suspect that will involve fleshing out some of the memory management
issues around dynamic decimals, as touched on here:
http://www.bytereef.org/mpdecimal/doc/libmpdec/memory.html#static-and-dynamic-decimals

On Mon, Apr 9, 2012 at 3:33 PM, stefan.krah <python-checkins at python.org> wrote:
> http://hg.python.org/cpython/rev/170bdc5c798b
> changeset:   76197:170bdc5c798b
> parent:      76184:02ecb8261cd8
> user:        Stefan Krah <skrah at bytereef.org>
> date:        Mon Apr 09 20:47:57 2012 +0200
> summary:
>  Resize the coefficient to MPD_MINALLOC also if the requested size is below
> MPD_MINALLOC. Previously the resize was skipped as a micro optimization.
>
> files:
>  Modules/_decimal/libmpdec/mpdecimal.c |  36 ++++++++------
>  1 files changed, 20 insertions(+), 16 deletions(-)
>
>
> diff --git a/Modules/_decimal/libmpdec/mpdecimal.c b/Modules/_decimal/libmpdec/mpdecimal.c
> --- a/Modules/_decimal/libmpdec/mpdecimal.c
> +++ b/Modules/_decimal/libmpdec/mpdecimal.c
> @@ -480,17 +480,20 @@
>  {
>     assert(!mpd_isconst_data(result)); /* illegal operation for a const */
>     assert(!mpd_isshared_data(result)); /* illegal operation for a shared */
> -
> +    assert(MPD_MINALLOC <= result->alloc);
> +
> +    nwords = (nwords <= MPD_MINALLOC) ? MPD_MINALLOC : nwords;
> +    if (nwords == result->alloc) {
> +        return 1;
> +    }
>     if (mpd_isstatic_data(result)) {
>         if (nwords > result->alloc) {
>             return mpd_switch_to_dyn(result, nwords, status);
>         }
> -    }
> -    else if (nwords != result->alloc && nwords >= MPD_MINALLOC) {
> -        return mpd_realloc_dyn(result, nwords, status);
> -    }
> -
> -    return 1;
> +        return 1;
> +    }
> +
> +    return mpd_realloc_dyn(result, nwords, status);
>  }
>
>  /* Same as mpd_qresize, but the complete coefficient (including the old
> @@ -500,20 +503,21 @@
>  {
>     assert(!mpd_isconst_data(result)); /* illegal operation for a const */
>     assert(!mpd_isshared_data(result)); /* illegal operation for a shared */
> -
> -    if (mpd_isstatic_data(result)) {
> -        if (nwords > result->alloc) {
> -            return mpd_switch_to_dyn_zero(result, nwords, status);
> -        }
> -    }
> -    else if (nwords != result->alloc && nwords >= MPD_MINALLOC) {
> -        if (!mpd_realloc_dyn(result, nwords, status)) {
> +    assert(MPD_MINALLOC <= result->alloc);
> +
> +    nwords = (nwords <= MPD_MINALLOC) ? MPD_MINALLOC : nwords;
> +    if (nwords != result->alloc) {
> +        if (mpd_isstatic_data(result)) {
> +            if (nwords > result->alloc) {
> +                return mpd_switch_to_dyn_zero(result, nwords, status);
> +            }
> +        }
> +        else if (!mpd_realloc_dyn(result, nwords, status)) {
>             return 0;
>         }
>     }
>
>     mpd_uint_zero(result->data, nwords);
> -
>     return 1;
>  }
>
>
> --
> Repository URL: http://hg.python.org/cpython
>
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