(gamma-random-float>1) ( alpha beta -- n )

Vocabulary

random.private

Inputs

alpha	an object
beta	an object

Outputs

n

an object

Definition

USING: combinators.short-circuit kernel math math.functions
namespaces random ;

IN: random.private

:: (gamma-random-float>1) ( alpha beta -- n )
    random-generator get :> rnd 2.0 alpha * 1 -
    sqrt :> ainv alpha 4.0 log - :> bbb alpha ainv +
    :> ccc 0 :> r! 0 :> z! 0 :> result! [
        r
        { [ 1.0 4.5 log + + z 4.5 * - 0 >= ] [ z log >= ] } 1||
        not
    ] [
        rnd (random-unit) :> u1 rnd (random-unit) :> u2 u1 1.0
        u1 - / log ainv / :> v alpha v e^ * :> x u1 sq u2 *
        z! bbb ccc v * + x - r! x beta * result!
    ] do while result ;