MeatAxe
2.4

zad [Options] []Mat []Mat ... Result
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 $D=ABC$. 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 $C=AB$, 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