Section VII - file Storage Requirements

Depending on the requirements of a run, NEC-2 may use the following files.

11,12,13,14,15,16 - scratch files for matrix manipulations.

20 - NGF file

21 - Sommerfeld/Norton data.

The scratch files are used only when the matrix will not fit into core stroage. Fro a case that does not use the NGF (but may write a NGF file), there are five options for matrix storage. IF

N=the number of equations (number of segments plus twice the number of patches),

N_x=the number of equations for a symmetric section, and

I_R=number of complex numbers for the matrix in core storage (4000),

then the case, indicated by the value of ICASE in the code, are

1. matrix in core, no symmetry (N² <=I_R).
2. matrix in core,symmetry (NN_x <=I_R).
3. matrix in core, no symmetry (N² >=I_R).
4. matrix in core,symmetry blocks fit in core (NN_x > I_R,N_x²<=I_R).
5. matrix out of core,symmetry blocks do not fit in core N_x²>I_R).

File storage is used in cases 3,4 and 5. Only the four files (11,12,13 and 14) are used when the NGF is not in use. The size of each file is approximately @NN_x words. If the computer system requires that the user specify the file size, a safety margin should be included in the request. A more accurate estimate of the file size is

L=2NN_c[N_x/N_c],

Where

N_c=[I_R)/(2N)]

and [ ] indicates truncation. N_c, which is the number of matrix columns in I/O block, must be at least 1.

When the NGF is used, all six scratch files may be required. For the NGF the matrix is partitioned into four sections as

    _   _

    |A  B|

    |C  D|

    -   -

A is the matrix for the NGF structure and is factored before the NGFfile is written. The stroage case for A is indicated in the NGFlable by the value of ICASE (see exampel 10 in section IV). When the NGF is used, matrix A is read from file 20 and, if ICASE is 3,4, or 5, is stored on file 13. The size of file 13 when the NGF is used is approximately:

   ICASE            Length of file 13

       3                4N

² 4 2NN_x 5 4NN_x There are four options for storage of the matrices B, C, and D. these are associated with the integer ICASX as follows:
ICASE

1. A_R, B, C, and D fit in core together where
   A_R=A for ICASE=1 or 2,
   =one I/O block of A for ICASE=3 or 5,
   =one submatrix for ICASE=4
2. B, C, an dD fit in core but not with A_R. This is possible only for ICASE=3, 4, or 5 when A does not need dedicated space in core. A_R an dB must also fit in core together.
3. B, C, and D do not fit in core, but D fits in core alone.
   A and D must fit together if ICASE=1 or 2.
4. D does not fit in core.

The sizees of matrices B, C, and D depend on the number of new unknowns N_n where

N_n=N_n+N_t+2N_p+10N_q

N_s=number of new segments added to NGF,

N_t=number of NGF segments connected to new segments or patches,

N_p=number of new patches,

N_q=number of NGF patches connected to new segments.

The sizes of matrices B and C are 2NN_n and the size of D is 2N_n² words. The file lengths are approximately 2N_n² words for files 11 and 12 and 2NN_n for files 14, 15 and 16. when ICASX is 1 these files are not used, and when ICASX is 2 file 16 is not used.

The length of the NGF file (20) is approximately 4N(N_x+3). The length of the Summerfeld/Norton data file (21) is about 2200 words.