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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 =< 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 4)
                 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,
                      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):  not used

     SDUM:     not used

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) 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.

• 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:

 *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
 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....+....8
 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)