MeatAxe
2.4

zsi [Options] Space1 Space2 Sum Int
This program reads in two spaces from Space1 and Space2 and writes out their sum and intersection, in semiechelon form, to Sum and Int, respectively. The input files must be matrices over the same field and with the same number of columns. They need not be in echelon form.
There must be enough memory to hold two copies of each of the two spaces at the same time.