added some Xorshift PRNGs of George Marsaglia

README.md

@@ -70,3 +70,9 @@ Mixed-radix [decimation-in-time](https://en.wikipedia.org/wiki/Cooley%E2%80%93Tu
 
 Some everyday helpers, like the [signum function](https://en.wikipedia.org/wiki/Sign_function) or the [lerp function](https://en.wikipedia.org/wiki/Linear_interpolation).
 
+### [xorshift.hh](xorshift.hh)
+
+Sometimes we need a sequence of ["random enough"](https://en.wikipedia.org/wiki/Diehard_tests) numbers but don't want to store them in an array to get a repeatable sequence.
+Here a [Pseudorandom number generator](https://en.wikipedia.org/wiki/Pseudorandom_number_generator) can help by prodiving a deterministic and thus repeatable sequence of numbers.
+[George Marsaglia](https://en.wikipedia.org/wiki/George_Marsaglia) discovered a class of simple and fast pseudorandom number generators, which he called [Xorshift](https://en.wikipedia.org/wiki/Xorshift).
+

xorshift.hh

@@ -0,0 +1,77 @@
+/*
+Class of pseudorandom number generators, discovered by George Marsaglia
+
+Copyright 2018 Ahmet Inan <inan@aicodix.de>
+*/
+
+#ifndef XORSHIFT_HH
+#define XORSHIFT_HH
+
+namespace DSP {
+
+class Xorshift32
+{
+	uint32_t y;
+public:
+	Xorshift32(uint32_t y = 2463534242) : y(y) {}
+	uint32_t operator()()
+	{
+		y ^= y << 13;
+		y ^= y >> 17;
+		y ^= y << 5;
+		return y;
+	}
+};
+
+class Xorshift64
+{
+	uint64_t x;
+public:
+	Xorshift64(uint64_t x = 88172645463325252) : x(x) {}
+	uint64_t operator()()
+	{
+		x ^= x << 13;
+		x ^= x >> 7;
+		x ^= x << 17;
+		return x;
+	}
+};
+
+class Xorwow
+{
+	uint32_t x, y, z, w, v, d;
+public:
+	Xorwow(uint32_t x = 123456789, uint32_t y = 362436069,
+		uint32_t z = 521288629, uint32_t w = 88675123,
+		uint32_t v = 5783321, uint32_t d = 6615241) :
+		x(x), y(y), z(z), w(w), v(v), d(d) {}
+	uint32_t operator()()
+	{
+		uint32_t t = x ^ (x >> 2);
+		x = y; y = z; z = w; w = v;
+		v = (v ^ (v << 4)) ^ (t ^ (t << 1));
+		d += 362437;
+		return d + v;
+	}
+};
+
+class Xorshift128
+{
+	uint32_t x, y, z, w;
+public:
+	Xorshift128(uint32_t x = 123456789, uint32_t y = 362436069,
+		uint32_t z = 521288629, uint32_t w = 88675123) :
+		x(x), y(y), z(z), w(w) {}
+	uint32_t operator()()
+	{
+		uint32_t t = (x ^ (x << 11));
+		x = y; y = z; z = w;
+		w = (w ^ (w >> 19)) ^ (t ^ (t >> 8));
+		return w;
+	}
+};
+
+}
+
+#endif
+