FLUKA: GLOBAL
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GLOBAL
Makes a global declaration about the present run, setting some
important parameters that must be defined before array memory
allocation
See also DEFAULTS, FIXED, FREE
Important: GLOBAL declarations, if present, must precede any executable
option
WHAT(1)
= maximum number of regions (must be =< 100000, see note 2)
Default
: 1000
WHAT(2)
= declaration of "how analogue" this run must be: fully
analogue, as biased as possible, or automatically chosen by
the program?
< 0.0: as analogue as possible (provided the input is
consistent with this choice)
> 1.0: as biased as possible (allowed also for a run in
which no explicit biasing option is requested: in
this case it simply means "do not try to be
analogue")
0.0 <= WHAT(2)
<= 1.0: as analogue as decided by the program
according to the selected biasing options
Default
: 0.0 (input decides the amount of biasing)
WHAT(3)
: declaration about the use of the DNEAR variable (see Note 4)
when computing physical steps:
= 0 --> use Dnear when computing the tentative length
of particle steps only when random seed
reproducibility is assured (full reproducibility
of random seeds within the same geometry package,
possible non reproducibilities among different
geometry packages describing the same geometry)
=-1 --> do not use Dnear when computing the tentative
length of particle steps (full reproducibility
of random seeds starting from different histories,
some penalty in CPU)
=-2 --> do not use Dnear at all
Default
: 0.0 (random number sequence reproducible within the
same geometry package)
WHAT(4)
: flag to request various types of input
< 0.0: resets the default
= 0.0: ignored
= 1.0: requests the use of names (alphanumerical 8-character
strings beginning by alphabetical) instead of numbers
as identifiers of particles, materials and regions in
the relevant "WHAT" fields of input commands. If fixed
format is used, each name must be contained inside
the corresponding 10-character field. If free-format,
name-based geometry input has not been requested (see
WHAT(5)
and Note 6), the region names, generated
automatically by FLUKA, can be found on standard output.
= 2.0: requests free-format input for all input commands (for
geometry body and region input, see WHAT(5)
). The six
"WHAT" fields must all be input, or replaced by two
successive separators (together with zero or more blanks)
= 3.0: the two previous options are both requested, i.e.
alphanumerical 8-character names are used to identify
particles, materials and regions in the relevant "WHAT"
fields of input commands, and free format is also used
(for geometry body and region input, see WHAT(5)
).
The six "WHAT" fields must all be input, or replaced by two
successive separators (together with zero or more blanks)
= 4.0: requests numerical format input for all input commands
Default
: 1.0 (name-based, fixed format input)
WHAT(5)
: flag to request free format in the geometry input for bodies
and regions. This format is described in 8}, and requires the
use of names (alphanumerical 8-character strings beginning by
alphabetical) as identifiers. Parentheses are allowed.
< 0.0: resets the default
= 0.0: ignored
> 0.0: geometry input for bodies and regions will be in free
format and name-based
Default
= -1. (numerical, fixed format geometry input)
WHAT(6)
: Requested blank common memory allocation (real*8 units),
meaningful only for compilers supporting F2003 features
and beyond (eg Gfortran)
SDUM
: in most cases there is no need for any SDUM
, however for
old inputs still containing deprecated bodies, the user can set:
= DEPRBODY: allows to use temporarily the deprecated body types,
ARB, BOX, WED
Notes:
1) In most cases the user should not worry about the number
of geometry regions. Despite the fact that FLUKA input
does not follow any specific order, the program is able to
manage initialisation of all geometry-dependent arrays
by allocating temporary areas of memory even before the
actual dimensions of the problem are known. The unused parts
of such areas are recovered at a later time when the whole
input has been read. However, if the number of regions is
very large (> 1000), the program needs to be informed in order
to increase the size of such temporary areas. This information
must be given at the very beginning: therefore GLOBAL
(together with DEFAULTS, MAT-PROP and PLOTGEOM) is a rare
exception to the rule that the order of FLUKA input cards is free.
2) For Fortran90 versions (eg Gfortran) supporting the standard
F2003 and beyond, all arrays depending on the number of regions
are allocated run time and this parameter is no longer relevant.
The "hard" limit of 100000 regions represents the maximum that
can be obtained without recompiling the program for the G77
version. It can be overridden, but only by increasing the
value of variable MXXRGN in the INCLUDE file DIMPAR and
recompiling the whole code. In this case, however, it is
likely that the size of variable NBLNMX in INCLUDE file
BLNKCM will have to be increased too.
3) In a "fully analogue" run, each interaction is simulated by
sampling each exclusive reaction channel with its actual
physical probability. In general, this is not always the case,
especially concerning low-energy neutron interactions.
Only issuing a GLOBAL declaration with WHAT(2)
< 0 can it
be ensured that analogue sampling is systematically carried
out whenever it is possible. The lack of biasing options in
input is not sufficient for this purpose. This facility should
be used in problems where fluctuations or correlations cannot
be ignored, but is likely to lead to longer computing times.
4) DNEAR designates the distance between the current particle
position and the nearest boundary (or a lower bound to that
distance), and it is used by FLUKA to optimise the step
length of charged particles. The concept and the name have
been borrowed from the EGS4 code, but the FLUKA implementation
is very different because it is fully automatic rather than left
to the user, and it is tailored for Combinatorial Geometry, where
a region can be described by partially overlapping sub-regions
(described in input by means of the OR operator).
The sequential order in which overlapping sub-regions are
considered when evaluating DNEAR is irrelevant from the point
of view of particle tracking, but can affect the random number
sequence. This does not have any effect on the average results
of the calculation, but the individual histories can differ due
the different random number sequence used. Option GLOBAL can be
used in those cases where the user wants to reproduce exactly
each particle history, or on the contrary to forgo it in order to
get a better step optimisation.
5) Free format can be requested also by option FREE, but only for
the part of input that follows the command. FREE cannot be used
to request free format geometry input. See the Notes to FREE
(Note 2 and following) for the rules governing separators.
6) Free-format, name-based geometry input can be requested also by
setting SDUM
= COMBNAME in command GEOBEGIN.
Example 1:
TITLE
A fully analogue run (no other commands precede this TITLE card)
GLOBAL 2000. -1. 1. 0. 0. 0.
Example 2:
TITLE
Full free-format input (no other commands precede this TITLE card)
GLOBAL 0.0 0.0 0.0 2.0 1.0 0.
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