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 optionWHAT(1)= maximum number of regions (must be =< 20000)Default: 1000WHAT(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 optionsDefault: 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 the same geometry)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 (seeWHAT(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, seeWHAT(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, seeWHAT(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 commandsDefault: 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-basedDefault= -1. (numerical, fixed format geometry input)WHAT(6): not usedSDUM: in most cases there is no need for anySDUM, however for old inputs still containing deprecated bodies, and/or, Flair expressions in the old format, the user can set: = DEPRBODY: allows to use temporarily the deprecated body types, ARB, BOX, WED, (see the release notes for more details) = OLDFLAIR: allows to use the Flair expression format at the user own risk (see the release notes for more details) = OLDFLBDY: as DEPRBODY and OLDFLAIR togetherNotes: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 20000 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 withWHAT(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 settingSDUM= 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.
Previous Index Next