This method multiplies a constant times a portion of a column
of a matrix and adds the product to the corresponding portion
of another column of the matrix --- a portion of col2 is
replaced by the corresponding portion of a*col1 + col2.
This method multiplies a constant times a portion of a column
of a matrix x[ ][ ] and adds the product to the corresponding portion
of a vector y[ ] --- a portion of y[ ] is replaced by the corresponding
portion of ax[ ][j] + y[ ].
This method multiplies a constant times a portion of a vector y[ ]
and adds the product to the corresponding portion
of a column of a matrix x[ ][ ] --- a portion of column j of x[ ][ ]
is replaced by the corresponding
portion of ay[ ] + x[ ][j].