# RE: RE: The maximum number of binnings in USRBIN

From: Anton Lechner <Anton.Lechner_at_cern.ch>
Date: Sun, 1 Sep 2013 16:29:48 +0000

Dear Chenyuan,

For clarity, I inserted different numbers in your Email below to refer to your specific questions. Here are my answers:

(1) When saying "number of USRBINs", I mean the number of USRBIN scorings you have in your input file (always counting the USRBIN card and its corresponding continuation card as *one* USRBIN) and *independently* which quantity you are scoring (energy deposition, fluence, etc.). For example, if you have following cards in your input file, it means you have two USRBIN scorings:
USRBIN 10. ELECTRON -30. 0.4 0.4 0.0221fluElec
USRBIN -0.4 -0.4 0.022 40.0 40.0 1.&
USRBIN 10. POSITRON -30. 0.4 0.4 0.0221fluPos
USRBIN -0.4 -0.4 0.022 40.0 40.0 1.&

(2) Let me illustrate this by means of the example given above: each USRBIN has 40*40*1=1600 bins, but since you have two USRBINs your total number of bins is 2*1600=3200. This means you need a memory allocation for 3200 bins. Of course, if you have further USRBINs, you need to determine the number of bins for each and add them up in the same way.

(3) This really depends what you actually want to calculate, i.e. what you intend to learn from the simulation. Just a hint: consider that if your geometry has a granularity of 6 mm in y and at the same time you have a rectangular homogeneous electron field of the same size (covering all 6 mm), then a 200 um bin size in y will not give you new information for most of the (central) bins, but only around the region boundaries. You may want to consider to use a more fine-grained binning only around boundaries. But I repeat myself, I really don't know what you actually want to get out of the simulation.

(4) I admit that I might have expressed myself not clear enough. It is not necessarily the difference between incident electron energy and transport cut-off/production cut which matters, but it is the artificial cut on electrons (in your case mostly on the secondary electrons) which you introduce by having these cuts. As you have a fluence scoring, it will of course change your result if you have lower cuts (since each electron is counted equally independent of its energy). Which cut you should choose once more depends on your physical problem.

(5-6) You did not attach any input file (in this context, please note that the manual is always a very valuable source of information)

Cheers, Anton

________________________________________
From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of yyc2011_at_mail.ustc.edu.cn [yyc2011_at_mail.ustc.edu.cn]
Sent: 01 September 2013 13:39
To: fluka-discuss_at_fluka.org
Subject: Re: RE: The maximum number of binnings in USRBIN

Dear Anton,

First, you say "maximum number of binnings" refers to the number of USRBINs I can have.What is the meaning?It means we can have many
usrbins,one of usrbin about energy deposition,one of usrbin about fluence,one of usrbin about neutron balance,and so on.I understand
it,Right?
(1)

Second,you say "It is not important how many bins you have per USRBIN, but how many you have in total for all USRBINs".I don't
understand what you say.Could you give me a example or a detailed explain?
(2)

Third,you say "your smallest geometric structure is 20 um in x and 6 mm in y, while you aim for a bin size of less than 1 um in both
x and y".At this point,I make some changes in my input file.In the new input file,the smallest geometric structure is still 20 um in
x and 6 mm in y,but my aim for a bin size of 4 um in x and 200 um in y.Do you think I was right in doing this?
(3)

Fourth, my primary electrons energy is 160 KeV.The transport cut-off energy is 100KeV for electrons.You ask me to consider if this
difference between primary energy and cut is sufficient for my problem.At this point,I want to know how can I estimate if this
difference between primary energy and cut is sufficient for my problem".
(4)

see my new input file.And,I will very happy if you give me some suggestions.
(5)

Fifth,you say "if I have such low primary electron energies and um geometries, I should consider applying single scattering."In my
new input file,I add the MULSOPT card.This is the first time I use this card.Could you see my input file?Is it wrong?Maybe You can
give me some examples.
(6)

Thanks for your time.Thanks for any suggestions.

Yours,
Chenyuan

> -----Original E-mail-----
> From: "Anton Lechner" <Anton.Lechner_at_cern.ch>
> Sent Time: 2013-8-31 19:30:33
> To: "yyc2011_at_mail.ustc.edu.cn" <yyc2011_at_mail.ustc.edu.cn>, "fluka-discuss_at_fluka.org" <fluka-discuss_at_fluka.org>
> Cc:
> Subject: RE: The maximum number of binnings in USRBIN
>
> Dear Chenyuan,
>
> You misunderstood the comment in the manual: "maximum number of binnings" refers to the number of USRBINs you can have and not to the number of bins (see Manual: "A 'binning' is a regular spatial mesh"). The number of bins you can have is limited by the memory available for scorings:
> *) See following answer on the FLUKA discuss list: http://www.fluka.org/web_archive/earchive/new-fluka-discuss/5260.html: the memory allocation is hard-wired in the library and is 360 MB
> *) It is not important how many bins you have per USRBIN, but how many you have in total for all USRBINs
> *) Your mesh of 10000*10000*1 occupies 800 MB and is hence far beyond the limit of allocated memory
>
> Apart from this, I have some further comments:
> *) Even if such a large number of bins would be possible, you should ask yourself if it would make sense. First, your smallest geometric structure is 20 um in x and 6 mm in y, while you aim for a bin size of less than 1 um in both x and y. Secondly, such a large number of bins would probably be challenging in terms of statistical error.
> *) Your primary electrons have an energy of 160 keV, but the transport cut-off and production threshold set by PRECISIO is 100 keV. You should ask yourself if this difference between primary energy and cut is sufficient for your problem. You can set lower cut values with the EMFCUT card.
> *) Note that if you have such low primary electron energies and um geometries, you should consider applying single scattering. I also quote the FLUKA manual: "The minimum recommended energy for PRIMARY electrons is about 50 to 100 keV for low-Z materials and 100-200 keV for heavy materials, unless the single scattering algorithm is used. Single scattering transport allows to overcome most of the limitations at low energy for the heaviest materials at the price of some increase in CPU time."
>
> Cheers, Anton
>
>
>
> ________________________________________
> From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] on behalf of yyc2011_at_mail.ustc.edu.cn [yyc2011_at_mail.ustc.edu.cn]
> Sent: 31 August 2013 05:19
> To: fluka-discuss_at_fluka.org
> Subject: The maximum number of binnings in USRBIN
>
> Dear Fluka experts,
>
> I have a question about the maximum number of binnings that I can define in USRBIN.It seems to go wrong when I set the number of
> binnings=10000 or 8000 in my input file.But when I set the number of binnings=1000,it runs normal. Meanwhile,I note in the Fluka
> manual"The maximum number of binnings that the user can define is 400. This value can be changed by modifying the parameter MXUSBN
> in member USRBIN of the flukapro library or directory and then re-compiling and linking Fluka." In the manual,It says the maximum
> number of binnings that the user can define is 400.But when I set the number of binnings=1000,I do not modify the parameter
> MXUSBN.But the fluka runs normal.The attachments are my input file and .out file.Could you help me?
>
> Thanks for any suggestions.
>
> Yours
> Chenyuan
>
Received on Mon Sep 02 2013 - 09:23:15 CEST

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