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A Data Input Program (MFI) for the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model
U.S. Geological Survey Water-Resources Investigations Report 94-468

Memory Usage

MFI stores the data that it reads in memory. Like MODFLOW, MFI uses a single array, X, to store most of its data. Locations of various parameters within X are maintained by MFI. Instead of having a separate variable that locates each parameter in X, MFI maintains a list of parameter names and their locations. The list is searched whenever the location of a parameter is needed.

Lists of stress data for a stress period require special consideration because MFI does not require the maximum size of a list to be specified. MFI allows the user to enter list data of varying length, and the length can change at any time. In order to store lists of varying size, MFI allocates memory for lists in blocks. Each block has a fixed size, but a list can consist of up to 10 blocks.

The following parameters control how much memory MFI can use. These parameters are defined in the file "mfi.gbl," which is an include file used in many of MFI's subroutines. In addition to the size of the X array, these parameters specify the sizes of a number of other arrays used by MFI to keep track of data.

LENX -- Number of elements in the X array
MXVAR -- Maximum number of parameters
MXARR -- Maximum number of parameters that are arrays
MXFNAM -- Maximum number of files
MXLIST -- The number of entries in a list block; a list can consist of up to 10 blocks

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