Anssi Seppälä wrote: > I have two big 2-dimensional arrays in mapped files A and B. I need > to calculate +/ A * B efficiently and without "out of memory". > In the case A was a vector the . (dot) can make it +/ . * , but this > does not work if A is a matrix. Is there a way to do this without a > program loop?
A +/@:* B but that should have the same memory requirements as the original Other formulations are possible (for example: +/ .*"1&.|:), but maybe for memory issues you'd best use a loop (ideally, one over very large chunks of data, to amortize the cost of executing J's primitives). -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
