[erlang-questions] io_lib:format R16B03 performance and jsx impact

Lukas Larsson <>
Tue Jan 28 10:54:01 CET 2014


Hello,

The code for formatting float when doing it through io_lib:format it
written in pure Erlang. The reason that io_lib:format is implemented in
Erlang is because it allows much greater cross platform formatting
capabilities, alas at the cost of performance.

Why you see a performance drop in between R15B03 to R16B03 I don't know, if
you could create a minimal reproducible benchmark that shows the difference
that would be great.

If you want to have a speedy conversion of something you know is a float to
a textual format you should use float_to_list/binary as that is meant to be
a fast conversion, but with less flexibility.

Lukas


On Tue, Jan 28, 2014 at 10:05 AM, Max Lapshin <> wrote:

> btw, why io_lib:format is so slow? simple changing it to nif with fprintf
> reduces cpu a lot.
>
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