[erlang-questions] R11B-5 vs R12B-1: Win32 CPU Usage?

Kenneth Lundin <>
Tue Apr 1 15:20:53 CEST 2008

Hi Jan,

(strange!, this is the second time I see exactly the same mail from you and give
the same answer, didn't you see my previous answer?)

On 3/26/08, Jan Jacobs <> wrote:
> Yesterday I decided to change from R11B-1 to R12B-1 and had the following
> issues:
> 1) erl_interface libraries requires Visual Studio 2005 (Not documented at
> all)

I agree with you that this could have been mentioned in the release notes.
There are no significant changes in the erl_interface code that
requires Visual Studio 2005 it is just that we where forced to upgrade
from the ancient MSVC we used to build with before because of the SMP
support for Windows intruduced in R12B.
We therefore build all the C-binaries with the same compiler from MSVS 2005
even if it is not really required for erl_interface.
If you need erl_interface built with another compiler i think it is
pretty straight forward to do that yourselves.
You can also link your C program with erl_interface from R11B and run it towards
the R12B system, I see no reason for this to cause problems.

> 2) R12B-1 consumes more CPU time than R11B-1.

I am not sure (rather the opposite) that the CPU time is a relevant measure.
The interesting question is if your application executes significantly slower
under R12B-1 than under R11B. If that is the case we can investigate why.

It is also important to know if you have recompiled all your modules
with the R12B
compiler and also if you are running the SMP or non SMP version of the
Erlang VM.
On multicore machines as well as hyperthreaded ones the SMP version will
be started as default.

As far as we know the R12B version should be slightly faster than the
R11B version
on Windows.

/Regards Kenneth, Erlang/OTP team Ericsson

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