Makes a global declaration about the present run, setting some
important parameters that must be defined before array memory
allocation
Note: GLOBAL declarations, if present, must precede any executable
option
WHAT(1) = maximum number of regions (must be =< 10000)
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
below) when computing physical steps:
< 0 --> always use DNEAR when computing the tentative
length of particle steps (it can cause non
reproducibility of the random number sequence when
starting from different histories, but it does not
affect physics)
> 0 --> do not use DNEAR when computing the tentative
length of particle steps (full reproducibility
of the random number sequence starting from different
histories, some penalty in CPU)
= 0 --> (default) use DNEAR when computing the tentative
length of particle steps only when random
seed reproducibility is assured (full reproducibility
of the random number sequence within the same
geometry package, possible non reproducibilities
among different geometry packages describing
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
geometry input has not been requested (see WHAT(5)) 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
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
WHAT(6): not used
SDUM: not used
Notes: 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.
The "hard" limit of 10000 regions represents the maximum that
can be obtained without recompiling the program. 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.
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.
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.
Example 1:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
TITLE
A fully analogue run (no other commands precede this TITLE card)
GLOBAL 2000. -1. 1. 0. 0. 0.
* This run needs more than the default maximum number of regions. It is
* requested to be as analogue as possible and to avoid using DNEAR if
* it risks to affect the random number sequence.
Example 2:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
TITLE
Full free-format input (no other commands precede this TITLE card)
GLOBAL 0.0 0.0 0.0 2.0 1.0 0.
* The following input will be all in free format (both the FLUKA commands
* and the geometry description)
