rand: add full precision f32 and f64 random functions; fix f32/f64 multipliers (#16875)

vlib/rand/fp_test.v

@@ -0,0 +1,116 @@
+import rand
+
+struct Histo {
+mut:
+	lo f64
+	ct int
+}
+
+const (
+	// The sample size to be used; keep cpu time less than 5 seconds
+	count = 9100100
+	// Two sets of seeds
+	seeds = [[u32(2742798260), 2159764996], [u32(2135051596), 958016781]]
+)
+
+fn test_f32() {
+	mut histo := []Histo{}
+	mut candidate := f32(0.0)
+
+	histo << Histo{1.0e-9, 0}
+	histo << Histo{1.0e-6, 0}
+	histo << Histo{1.0e-4, 0}
+	histo << Histo{1.0e-2, 0}
+	histo << Histo{1.0e00, 0}
+
+	for seed in seeds {
+		rand.seed(seed)
+		for _ in 0 .. count {
+			candidate = rand.f32()
+			for mut p in histo {
+				if candidate < p.lo {
+					p.ct += 1
+				}
+			}
+		}
+	}
+	println(' f32  ')
+	println(histo)
+	assert histo[0].ct == 1
+	assert histo[1].ct == 16
+	assert histo[2].ct == 1802
+	assert histo[3].ct == 181963
+	assert histo[4].ct == 18200200
+	for mut p in histo {
+		p.ct = 0
+	}
+	for seed in seeds {
+		rand.seed(seed)
+		for _ in 0 .. count {
+			candidate = rand.f32cp()
+			for mut p in histo {
+				if candidate < p.lo {
+					p.ct += 1
+				}
+			}
+		}
+	}
+	println(' f32cp')
+	println(histo)
+	assert histo[0].ct == 0
+	assert histo[1].ct == 16
+	assert histo[2].ct == 1863
+	assert histo[3].ct == 142044
+	assert histo[4].ct == 18200200
+}
+
+fn test_f64() {
+	mut histo := []Histo{}
+	mut candidate := f64(0.0)
+
+	histo << Histo{1.0e-9, 0}
+	histo << Histo{1.0e-6, 0}
+	histo << Histo{1.0e-4, 0}
+	histo << Histo{1.0e-2, 0}
+	histo << Histo{1.0e00, 0}
+
+	for seed in seeds {
+		rand.seed(seed)
+		for _ in 0 .. count {
+			candidate = rand.f64()
+			for mut p in histo {
+				if candidate < p.lo {
+					p.ct += 1
+				}
+			}
+		}
+	}
+	println(' f64  ')
+	println(histo)
+	assert histo[0].ct == 0
+	assert histo[1].ct == 23
+	assert histo[2].ct == 1756
+	assert histo[3].ct == 182209
+	assert histo[4].ct == 18200200
+	for mut p in histo {
+		p.ct = 0
+	}
+	for seed in seeds {
+		rand.seed(seed)
+		for _ in 0 .. count {
+			candidate = rand.f64cp()
+			for mut p in histo {
+				if candidate < p.lo {
+					p.ct += 1
+				}
+			}
+		}
+	}
+	println(' f64cp')
+	println(histo)
+	assert histo[0].ct == 0
+	assert histo[1].ct == 17
+	assert histo[2].ct == 1878
+	assert histo[3].ct == 181754
+	assert histo[4].ct == 18200200
+}