Macro pg_sw 

macro_rules! pg_sw {
    ($input: expr, $pgc: expr, $all: expr, $size:tt, $lim: expr) => { ... };
}

Memory economic version of pg macro.

Since pg_sw, space wise prime generator, uses less space, it allows to generate larger prime numbers compared to pg.

Memory demands are reduced by one half. pg is considered to be time wise implementation.

In contrary to pg, this macro cannot significantly gain from proper target type choice.

Check with pg for guidelines.