universal_mult_hash Function

    elemental function universal_mult_hash( key, seed, nbits ) result( sample )
!! Version: experimental
!!
!! Uses the "random" odd 64 bit integer `seed` to map the 64 bit integer `key` to
!! an unsigned integer value with only `nbits` bits where `nbits` is less than 64.
!! ([Specification](../page/specs/stdlib_hash_procedures.html#universal_mult_hash-maps-an-integer-to-a-smaller-number-of-bits_1))

        integer(int64), intent(in) :: key
        integer(int64), intent(in) :: seed
        integer, intent(in)        :: nbits
        integer(int64)             :: sample

        sample = ishft( key*seed, -64 + nbits )

    end function universal_mult_hash