[neutron-mc] L_monitor.comp

[Peter Willendrup]

Hello Philip and mcstas users

On Mon, 24 Mar 2003, Philip Wilk wrote:

> Which version of L_monitor.comp I should be
> using? I am using the mcstas version 1.6.4d executable and the 1.6.4e
> library. I am runing it all on a Win2K box with with free bcc compiler.

Regarding the 1.6.4 series: Everyone should notice that this is not a
publicly available release - but a development version which has been
provided to selected users for testing only. Bugs should be expected
with this version, to be fixed in the oncomming official mcstas-1.7
version.

> This version includes a L_monitor.comp version 1.16, however,
> the MCSTAS website lists a version L_monitor.comp 1.4 for use with the
> MCSTAS 1.5 distribution. Now if this is not all confusing enough, I
> aways get a non-fatal "sqrt: DOMAIN error" when using either version.
> I have tracked it down to the "L_p[i] += p;" line in L_monitor.comp .
> It seems to still work fine, and sometimes when running the compiled
> simulation binary, I do not get this error; then when I run it again,
> I get the error. It always seems to generate reasonable results even
> with the error.
>
> I would really apprciate any insight or advice.

Here is a slightly technical answer to your question: In the 1.4 and 1.5
releases of mcstas, the L_N of neutron array was an int array. Event
counts were later moved to double to pass the '1e9' long limit.
This probably generates some alignement errors, that may be related to
that sqrt error... We will ofcourse look into the problem, applying a fix
to the code in the oncommming 1.7 release.

To indicate a possible timeframe for the next release, note that Emmanuel
Farhi and I are in the process of 'code freeze' - only very few more
features will go into our current development version. Next, we'll have to
do some more testing plus updates of the documentation...

Regards,

Peter Willendrup

--
-------------------------------------
Peter Kjaer Willendrup, Cand. Scient

Phone: (+45) 46 77 58 62
email: peter.willendrup at risoe.dk
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