Xorshift* 1024 (essential fragment)

gistfile1.go

var s0 = [16]uint64{
	0xEA221D1E5C8DB483,
	0xF89369282348A220,
	0x7022326276090608,
	0x1618FCC12E583E30,
	0xF7E7C005F85EFC69,
	0x132B746F9C2FF047,
	0x338324A69CBDC6B5,
	0x2B91B21FAAB58FE0,
	0x85CB192105B8B12B,
	0x5A9EC4772C1B642D,
	0xFEA936CB4A0CEA20,
	0x6865516844ED9BBD,
	0x16C12E5DCC3D7365,
	0x0BBDE3B5363FA6E9,
	0xD454C1D29E450885,
	0x480EB817028DB197,
}

type xorshiftstar struct {
	s [16]uint64
	p uint8
}

// global instance
var (
	s   = s0                  // copy reference init state.
	xss = &xorshiftstar{s, 0} // global instance uses s
)

/// algorithm /////////////////////////////////////////////////////////////

// NOTICE-BEGIN - original source: Xorshift - wikipedia.org. adapted for Go.
const xss_magic = uint64(1181783497276652981)

const (
	shift_A = 31 // 23
	shift_B = 11 // 17
	shift_C = 30 // 30
)

func (s *xorshiftstar) next() uint64 {
	var s0 = s.s[s.p]
	s.p = (s.p + 1) & 0xF
	var s1 = s.s[s.p]

	s1 ^= s1 << shift_A
	s1 ^= s1 >> shift_B
	s0 ^= s0 >> shift_C

	// update state
	s.s[s.p] = s0 ^ s1

	return s.s[s.p] * xss_magic
}

// NOTICE-END - original source: Xorshift - wikipedia.org. adapted for Go.

/// api ///////////////////////////////////////////////////////////////////