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1996-03-15
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News on the TSMATR matrix package by Timo Salmi in reverse order
================================================================
University of Vaasa, Finland, Linux Pentium garbo.uwasa.fi has a
large collection of Shareware, Freeware and Public Domain PC
programs available by anonymous FTP, WWW (World Wide Web) and mail
server. The file ftp://garbo.uwasa.fi/pc/ts/0news-ts contains news
about the TS-programs in the /pc/ts directory (in reverse order).
This text, which you now have, is an extract from the 0news-ts file
and the Usenet news.
....................................................................
Prof. Timo Salmi Co-moderator of news:comp.archives.msdos.announce
Moderating at ftp:// & http://garbo.uwasa.fi archives 193.166.120.5
Department of Accounting and Business Finance ; University of Vaasa
ts@uwasa.fi http://uwasa.fi/~ts BBS 961-3170972; FIN-65101, Finland
....................................................................
Fri 15-Mar-96: I have made an update of one of my old mathematical
packages now to be
ftp://garbo.uwasa.fi/pc/ts/tsmatr12.zip
Standard matrix calculations. Product, inverse, etc.
The programs are functionally unchanged, but I have brought the
information material in the package up to date. I have also added
the standard FILE_ID.DIZ identification file into the package. As
you probably know, many BBS systems display the contents of these
comment files on their file lists.
Corrected a small bug in MATMUL matrix multiplication. The
program now asks for confirmation if break is pressed. Another small
correction is that the MATMUL program takes up less memory than
before.
Sat 24-Mar-90: I have updated the set of my matrix calculation
programs. The new release is (/pc/ts/)tsmatr11.arc. This package
contains the matrix operations, which are solving simultaneous
linear equations (lineq.exe), calculating the inverse of a square
matrix (matinv.exe), and multiplying two matrixes (matmul.exe). The
maximum number of the simultaneous equations is 30, and the maximum
dimension in the matrix inversion program is 25x25. There must be
innumerable such programs around, and the algorithms used have
nothing much out of the ordinary. They are based on the Turbo Pascal
Numerical Toolbox, which has been used in accordance with Borland's
license.
There is one trick of mine, however, in these programs, which is
often lacking even in commercial packages. This is checking the
feasibility of the results. What I do is calculate a deviation
measure as follows. Let A denote the original square matrix, B the
inverse computed by the program, I and identity matrix. First the
matrix A*B-I is calculated, and then the sum of the absolute values
of the elements of this matrix. This is what I call the deviation
from unity. I have found this to be a very handy test of reliability
of the results especially in case of problematic matrixes.
Nevertheless, the main feature of this package is my user
interface (in programming terms the parser I've built). The
simultaneous equations are given in what is called an "as-is" or
"equations" format. This means that you can input e.g.
2x + 7.8y + 5.0z = 13.4
3x - 8.9y - z = 18.3
-x + 5.6 - 1.3 = 10.3
directly to the lineq.exe program, from file or from keyboard. If
you give the input from the keyboard you now have full line editing
potential with CursorRight, CursorLeft, BackSpace, Del, Home, End,
Insert, and Escape keys. Furthermore, there is input recall (using
the PageUp key), and orderly break at any time with the ctrl-C or
the break key. I have also corrected a bug in lineq.exe, which
prevented using the continuation line potential. This potential
means that you can write e.g.
2x + 7.8y &
+ 5.0z = 13.4
Also updated the directory routine, which can be invoked from within
lineq.exe if the input file is not found.