NEC-LIST: disk space for file

> Can anyone tell me how to compute precisely how much free disk space
> is required to run a NEC4D model having N wire segments (no patches)
> when N is greater than MAXMAT?

The matrix is divided into blocks so that two blocks fit into the array
of MAXMAT**2 complex numbers. Hence the number of columns of N complex
numbers in a block is

Nc=[MAXMAT**2/(2*N)]

where [] indicates truncation to an integer. The number of blocks is

Nb=[(N-1)/Nc] + 1

The last block may have a smaller number of columns than Nc so that
(Nb-1)*Nc + last block = N
but the size of the last block on the disk is the same as the others.
Hence the total number of bytes written is

Bytes written to file = Nn*Nb*Nc*N

where Nn is the number of bytes in a complex number: 8 for single
precision and 16 for double precision. The actual size of the file
will be a little bigger than this due to "other stuff" the system
writes into the file, so a precise estimate is difficult.

NEC-2 uses four sequential access files rather than the single direct
access file used by NEC-4, so four times as much disk space will be
needed with NEC-2. System virtual memory will probably be a better
choice in this case if it is available.

Jerry Burke
LLNL
Received on Wed Oct 23 1996 - 07:14:42 EDT