# zad man page

zad — add or subtract matrices

## Synopsis

**zad** [Options] [-]*<Mat>* [-]*<Mat>* ... *<Result>*

## Description

This program reads two or more input matrices, calculates their sum or difference and writes the result to a file. The input matrices must be compatible, i.e., they must be over the same field and have the same dimensions. **Zad** is designed to work with very large matrices without running out of memory. Only two rows are allocated as working memory.

By default, all input matrices are added. For example,

zad A B C

calculates the sum of A and B, and writes the result to C. If a file name is preceeded by a minus sign, this matrix is subtracted. For example,

zad A -B -C D

calculates *D*=*A*-*B*-*C*. To subtract the first matrix, you must insert an extra "--" before the file names. Otherwise the first argument would be interpreted as a program option. For example, to calculate *C*=-*A*-*B*, use

zad -- -A -B C

If a file name starts with "-", preceed the file name by "+" to add, or by "-" to subtract the matrix. If, for example, the second input file is "-B", use the following syntax:

zad A +-B C

zad A --B C

## Options

**-Q**- Quiet, no messages.
**-V**- Verbose, more messages.
**-T***<MaxTime>*- Set CPU time limit

## Input Files

*Mat*...- Input matrix or matrices.

## Output Files

*Result*- Sum of the input matrices.