Re: [PATCH] Re: Bignum performance

[Ihor Radchenko]

Po Lu <luangruo@yahoo.com> writes:

>>> And we have huge overheads converting things back-and-forth
>>> between GMP and Elisp formats. It is by choice. And my patch
>>> did not do anything about this difference.
>
> AFAIU, no conversion takes place between ``Elisp formats'' and GMP
> formats.  Our bignums rely on GMP for all data storage and memory
> allocation.

Thanks for the clarification!
So, GMP is not as fast as SBCL's implementation after all.
SBCL uses https://github.com/sbcl/sbcl/blob/master/src/code/bignum.lisp
- a custom bignum implementation, which is clearly faster compared to
GMP (in the provided benchmark):

perf record  ~/Git/emacs/src/emacs -Q -batch -l /tmp/fib.eln
0.739 s
(0.007 s for SBCL)

    17.11%  emacs    libgmp.so.10.5.0      [.] __gmpz_sizeinbase
     7.35%  emacs    libgmp.so.10.5.0      [.] __gmpz_add

^^ already >0.1 sec.

     6.51%  emacs    emacs                 [.] arith_driver
     6.03%  emacs    libc.so.6             [.] malloc
     5.57%  emacs    emacs                 [.] allocate_vectorlike
     5.20%  emacs    [unknown]             [k] 0xffffffffaae01857
     4.16%  emacs    libgmp.so.10.5.0      [.] __gmpn_add_n_coreisbr
     3.72%  emacs    emacs                 [.] check_number_coerce_marker
     3.35%  emacs    fib.eln               [.] F666962_fib_0
     3.29%  emacs    emacs                 [.] allocate_pseudovector
     2.30%  emacs    emacs                 [.] Flss

-- 
Ihor Radchenko // yantar92,
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