Re: how do I create a table with known big size?

["Jasper Klein" <jasper@...>]

Op Tue, 26 May 2020 18:33:50 +0200 schreef Andrea  
<andrea.l.vitali@gmail.com>:

> Let's say I know I need to create a big table and I do not want rehashes  
> to
> happen when I am filling it.
>
> What is the best way in Lua to create the big table?
>
> Is there any way to create a big table with only the array or only the  
> hash
> part?
>
> This can be done with the C API but I am wondering if there is way in  
> Lua.
> It seems not but maybe I missed something.
>
> I can only think about big constructors list in the source code - but  
> there
> is a limit on how big they can be right?
>
>     Andrea

Well, about 2 years ago I posted a patch for Lua 5.3.5 that exposed a  
function that can
reserve memory for the array and hash part of a table. [1]
The performance improvement can be significant when reserving the number  
of elements
that are expected for the hash part of a table, for the array part this is  
negligible.
Reserving avoids rehashing when the number of items in the hash part of  
the table grows
while filling the table.

Would be nice to see a similar function in a future release of Lua.

-- Jasper

[1] http://lua-users.org/lists/lua-l/2018-12/msg00175.html