The input of FLUKA consists of a text file containing a sequence of option lines (often called "cards") which are followed sometimes by data cards specific of the option (or command) requested. Option cards have all the same structure, and can be read in fixed format or in free format. A description of free format is given in 7}, options GLOBAL and FREE. Syntax: CODEWD, (WHAT(I), I = 1, 6),SDUM(the fixed format is A8, 2X, 6E10.0, A8) where: * CODEWD is the option keyword * The WHAT-parameters are numerical data (or logical data in numerical form) *SDUM, if present, contains character data (only in two exceptional cases, the STERNHEIme and WW-FACTOr options,SDUMcontains numerical information) Since 2006, a very practical and appealing feature has been introduced: INPUT BY NAMES. This means that the numeric WHAT fields can be filled with pre-defined or user-defined names, such as: - material names - particle or generalised particle names - region names, if the geometry too is written in free format "name" based - estimator names - detector/binning names Names must be at most 8 character long, with the exception of detector names (estimator options (USRBDX, USRTRACK, USRCOLL, USRBIN, USRYIELD, RESNUCLEi) which can be 10 character long. Leading and trailing blanks are automatically stripped, and the input parser is case sensitive. A special name (@LASTMAT, @LASTPAR, @LASTREG) can be used corresponding to the largest material number, particle id, and region number respectively. Name values and numeric values can both be used in the same input file, since the program is able to distinguish a numeric field from a character field. For this reason, names that can be interpreted as numbers must be avoided. This means that old numeric inputs need no modification. Fully-numeric interpretation, however, can be forced by means of the GLOBAL card. Due to the introduction of input by names, input data cards are no longer interpreted in the same order as in the input file, therefore the echo on standard output will look different from the original input. When using numeric fields, note that even if the values to be assigned to WHAT-parameters were logically integers, because of the format used they must be given with a decimal point. The order of the input cards is almost free, with the following exceptions: It can be preceded only by a GLOBAL card and by command TITLE. allowing multiple re-starts, only the first START command is executed now. Thus any input given after START is ignored, with the exception of USROCALL and STOP. after STOP is ignored. of information, not always in the standard format indicated above. These are: - OPEN is generally followed by the name of the file to be opened (scratch files are an exception) - DETECT, USRBIN, USRBDX, USRCOLL, USRTRACK, USRYIELD, EVENTBIN, EVENTDAT: data concerning user-defined detectors and binnings extend in general over two cards. The second card ("continuation card") must come after the first, but doesn't need to follow it immediately. A continuation card may be needed also for option GEOEND, when used to invoke the geometry debugger. - Input included between GEOBEGIN and GEOEND: geometry data must be given in a well-defined order and in a special format between a GEOBEGIN and a GEOEND definition (but the LATTICE and VOXELS geometry options, and the GEOBEGIN and GEOEND cards themselves follow the normal FLUKA format convention). - PLOTGEOM: Unless a different logical input unit is specified, the call to the PLOTGEOM program must be followed immediately by the PLOTGEOM input, in special format. - TITLE: the card following the TITLE command is considered as the title of the run and is reproduced in the output. - In some cases, the MAT-PROP option must be requested after the corresponding MATERIAL card. - The PLOTGEOM command must be issued after the geometry input, and, in case the user chooses to plot only boundaries between different materials, it must come also after all the ASSIGNMAt cards. It is also recommended that PLOTGEOM be issued before any biasing and any other option which makes use of permanent and/or temporary storage. Most definitions have some default values. If these are acceptable, it is not compulsory that the corresponding option card appear explicitly in the input sequence. Furthermore for most WHAT and/orSDUMparameters a default value (that may be different from the default value when the definition has not been input) is applied if the corresponding field is left blank (or set = 0.0) in the input card. Several option cards may appear more than once in the input sequence. In most cases, each of such additional cards obviously adds more definitions to those already given, provided they are different and not contradictory. In case of conflict, the last given generally overrides the previous one(s). This feature may be successfully exploited in the numerous cases where whole arrays are assigned according to the scheme: "From .... to .... in step of ...." (corresponding to a Fortran DO-loop) making the input more compact. An example can be found below in the description of option ASSIGNMAt, which is used to set a one-to-many correspondence between material numbers and region numbers. In most cases of such "DO-loop" assignments, especially when the same option card can be used to assign a value to more than one quantity, a blank or zero field does not assign the default value but leaves the previously given value unchanged. To remove any possible ambiguity, resetting the default value needs then to be done explicitly (generally -1. has to be input in such cases). "DO-loop" assignments can be used also when the input is name-based, since the program replaces each name by the corresponding numerical index. The correspondence can be found by examining the output frolm a short test run: however, it must be remembered that adding a new material, or a new region, will change the numerical sequence unless the new item is issued as the last of material or region definitions. In this case, if the "DO-loop" indicates all materials, or all regions, using the generic names @LASTMAT and @LASTREG makes a modification of the assignment definition unnecessary. All defaults and exceptions are listed under the description of each FLUKA input option. Different defaults, tuned to the type of application of interest, can be specified using the option DEFAULTS.
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