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Re: Optimizing ‘string=’
From: |
Andy Wingo |
Subject: |
Re: Optimizing ‘string=’ |
Date: |
Tue, 22 Jun 2010 22:51:13 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.0.92 (gnu/linux) |
Hi,
Nice profile-driven debugging :)
On Tue 22 Jun 2010 21:40, address@hidden (Ludovic Courtès) writes:
> @@ -1168,6 +1168,21 @@ SCM_DEFINE (scm_string_eq, "string=", 2, 4, 0,
> "value otherwise.")
> #define FUNC_NAME s_scm_string_eq
> {
> + if (SCM_LIKELY (scm_i_is_narrow_string (s1) == scm_i_is_narrow_string (s2)
> + && SCM_UNBNDP (start1) && SCM_UNBNDP (end1)
> + && SCM_UNBNDP (start2) && SCM_UNBNDP (end2)))
> + {
> + size_t len1, len2;
> +
> + len1 = scm_i_string_length (s1);
> + len2 = scm_i_string_length (s2);
> +
> + if (SCM_LIKELY (len1 == len2))
> + return scm_from_bool (memcmp (scm_i_string_chars (s1),
> + scm_i_string_chars (s2),
> + len1) == 0);
> + }
> +
Nasty, but OK I guess if you need it. Why not also add a fast path for
scm_is_eq (s1, s2), or for comparing stringbufs, or something ?
> It’s quite inelegant, but it leads to a more balanced profile:
>
> samples % symbol name
> 8079 23.3984 scm_string_eq
> 5649 16.3606 vm_debug_engine
> 5624 16.2882 scm_i_str2symbol
^ What is this doing here?
And for the matter, what are the rest about? Did you just do a really
short profile?
> 2840 8.2252 scm_ihashq
> 1755 5.0828 scm_i_string_hash
> 1637 4.7411 scm_fluid_ref
> 1027 2.9744 scm_i_string_ref
> 1011 2.9281 scm_hash_fn_get_handle
> 877 2.5400 scm_i_string_chars
> 793 2.2967 scm_module_variable
> 553 1.6016 scm_from_locale_stringn
> 471 1.3641 scm_from_stringn
> 426 1.2338 scm_sym2var
> 384 1.1121 scm_i_make_string
> 317 0.9181 scm_module_lookup
Andy
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