> and the latter may have runtime impact.
Definitely a concern for the "simple" case of a use-once regex. I was
thinking of something like (pseudo code)
var
=
:erlang.iolist_to_binary(["__regex_",:erlang.integer_to_list(abs(:erlang.monotonic_time(:nanosecond)))])
quote do
var = if var, do: var, else: Regex.compile!(binary_or_tuple, options)
end
Too much risk of performance impact? I think the BEAM optimises out the
binding in positive cases like this?
> Instead, we are discussing adding the optimization we did before directly
to Erlang/OTP
Yep, I'm anxiously awaiting a good outcome from that conversation :-)
Thanks for encouraging the OTP team on this.
On Sunday, March 30, 2025 at 12:54:32 AM UTC+11 José Valim wrote:
> The memoization will only be useful if we either do variable hoisting,
> which are inherently limited to the current function, or we store it in
> persistent term. The former will require meaningful changes in the compiler
> and the latter may have runtime impact.
>
> Instead, we are discussing adding the optimization we did before directly
> to Erlang/OTP. Meanwhile, I suggest refactoring the code to pass the regex
> around in sensitive areas. :(
>
>
>
> *José Valimhttps://dashbit.co/ <https://dashbit.co/>*
>
>
> On Sat, Mar 29, 2025 at 14:29 Kip <[email protected]> wrote:
>
>> TLDR;
>> Memoize (bind to a variable) the result of `Regex.compile!/2` on OTP 28
>> so that it is only compiled once.
>>
>> Background
>>
>> Since in OTP 28 it's not possible to unquote a regex (~r/..../) into
>> code, the implementation of sigil_r on OTP 28 has to compile the regex at
>> runtime. In code which iterates over text using regex (for example Unicode
>> break algorithm, Unicode transforms and so on) this could lead to a
>> performance penalty.
>>
>> Proposal
>>
>> Bind the result of Regex.compile!/2 to a variable called something like
>> `__regex_#{hash_of_regex_string}` if its successful. If the variable is
>> bound, use it directly without compilation. Do performance testing to
>> confirm that there is benefit to memoizing.
>>
>> I am fine to do this work if the proposal has merit.
>>
>>
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