June 2018 Update

Task/Unbias-a-random-generator/Aime/unbias-a-random-generator.aime

@@ -1,7 +1,7 @@
 integer
 biased(integer bias)
 {
-    return 1 ^ min(drand(bias - 1), 1);
+    1 ^ min(drand(bias - 1), 1);
 }
 
 integer
@@ -12,7 +12,7 @@ unbiased(integer bias)
     while ((a = biased(bias)) == biased(bias)) {
     }
 
-    return a;
+    a;
 }
 
 integer
@@ -23,21 +23,17 @@ main(void)
     n = 10000;
     b = 3;
     while (b <= 6) {
-        i = 0;
-        cb = 0;
-        cu = 0;
-        while (i < n) {
+        i = cb = cu = 0;
+        while ((i += 1) <= n) {
             cb += biased(b);
             cu += unbiased(b);
-
-            i += 1;
         }
 
         o_form("bias ~: /d2p2/%% vs /d2p2/%%\n", b, 100r * cb / n,
-	       100r * cu / n);
+               100r * cu / n);
 
         b += 1;
     }
 
-    return 0;
+    0;
 }

Task/Unbias-a-random-generator/Elena/unbias-a-random-generator.elena

@@ -0,0 +1,45 @@
+import extensions.
+
+int extension $op
+{
+    bool randN
+        = randomGenerator nextInt(self) == 0.
+
+    bool unbiased
+    [
+        bool flip1 := self randN.
+        bool flip2 := self randN.
+
+        while (flip1 == flip2)
+        [
+            flip1 := self randN.
+            flip2 := self randN.
+        ].
+
+        ^ flip1
+    ]
+}
+
+program =
+[
+    3 to:6 do(:n)<int>
+    [
+        int biasedZero := 0.
+        int biasedOne := 0.
+        int unbiasedZero := 0.
+        int unbiasedOne := 0.
+
+        0 till:100000 do(:i)
+        [
+            if (n randN) [ biasedOne += 1 ]; [ biasedZero += 1 ].
+            if (n unbiased) [ unbiasedOne += 1 ]; [ unbiasedZero += 1 ]
+        ].
+
+        console
+            printLineFormatted("(N = {0}):" padRight(17) + "# of 0"$9"# of 1"$9"% of 0"$9"% of 1", n);
+            printLineFormatted("Biased:" padRight(15) + "{0}"$9"{1}"$9"{2}"$9"{3}",
+                                    biasedZero, biasedOne, biasedZero / 1000, biasedOne / 1000);
+            printLineFormatted("Unbiased:" padRight(15) + "{0}"$9"{1}"$9"{2}"$9"{3}",
+                                    unbiasedZero, unbiasedOne, unbiasedZero / 1000, unbiasedOne / 1000).
+    ]
+].

Task/Unbias-a-random-generator/Java/unbias-a-random-generator-2.java

@@ -0,0 +1,28 @@
+// version 1.1.2
+
+fun biased(n: Int) = Math.random() < 1.0 / n
+
+fun unbiased(n: Int): Boolean {
+    var a: Boolean
+    var b: Boolean
+    do {
+        a = biased(n)
+        b = biased(n)
+    }
+    while (a == b)
+    return a
+}
+
+fun main(args: Array<String>) {
+    val m = 50_000
+    val f = "%d: %2.2f%%  %2.2f%%"
+    for (n in 3..6) {
+        var c1 = 0
+        var c2 = 0
+        for (i in 0 until m) {
+            if (biased(n)) c1++
+            if (unbiased(n)) c2++
+        }
+        println(f.format(n, 100.0 * c1 / m, 100.0 * c2 / m))
+    }
+}

Task/Unbias-a-random-generator/Julia/unbias-a-random-generator.julia

@@ -0,0 +1,20 @@
+randN(N) = () -> rand(1:N) == 1 ? 1 : 0
+function unbiased(biased::Function)
+    this, that = biased(), biased()
+    while this == that this, that = biased(), biased() end
+    return this
+end
+
+@printf "%2s | %10s | %5s | %5s | %8s" "N" "bias./unb." "1s" "0s" "pct ratio"
+const nrep = 10000
+for N in 3:6
+    biased = randN(N)
+
+    v = collect(biased() for __ in 1:nrep)
+    v1, v0 = count(v .== 1), count(v .== 0)
+    @printf("%2i | %10s | %5i | %5i | %5.2f%%\n", N, "biased", v1, v0, 100 * v1 / nrep)
+
+    v = collect(unbiased(biased) for __ in 1:nrep)
+    v1, v0 = count(v .== 1), count(v .== 0)
+    @printf("%2i | %10s | %5i | %5i | %5.2f%%\n", N, "unbiased", v1, v0, 100 * v1 / nrep)
+end

Task/Unbias-a-random-generator/REXX/unbias-a-random-generator.rexx

@@ -4,7 +4,7 @@ if #==''  |  #==","     then #=1000              /*#:  the number of SAMPLES to
 if R==''  |  R==","     then R=6                 /*R:  the high number for the  range.  */
 if datatype(seed, 'W')  then call random ,,seed  /*Specified?  Then use for RANDOM seed.*/
 dash='─';    @b="biased";         @ub='un'@b     /*literals for the SAY column headers. */
-say left('',5)   ctr('N',5)   ctr(@b)   ctr(@b"%")  ctr(@ub)  ctr(@ub'%')   ctr("samples")
+say left('',5)   ctr("N",5)   ctr(@b)   ctr(@b'%')  ctr(@ub)  ctr(@ub"%")   ctr('samples')
 dash=
        do N=3  to R;      b=0;                u=0
          do j=1  for #;   b=b + randN(N);     u=u + unbiased()

Task/Unbias-a-random-generator/Rust/unbias-a-random-generator.rust

@@ -0,0 +1,39 @@
+#![feature(inclusive_range_syntax)]
+
+extern crate rand;
+
+use rand::Rng;
+
+fn rand_n<R: Rng>(rng: &mut R, n: u32) -> usize {
+    rng.gen_weighted_bool(n) as usize // maps `false` to 0 and `true` to 1
+}
+
+fn unbiased<R: Rng>(rng: &mut R, n: u32) -> usize {
+    let mut bit = rand_n(rng, n);
+    while bit == rand_n(rng, n) {
+        bit = rand_n(rng, n);
+    }
+    bit
+}
+
+fn main() {
+    const SAMPLES: usize = 100_000;
+    let mut rng = rand::weak_rng();
+
+    println!(" Bias    rand_n  unbiased");
+    for n in 3..=6 {
+        let mut count_biased = 0;
+        let mut count_unbiased = 0;
+        for _ in 0..SAMPLES {
+            count_biased += rand_n(&mut rng, n);
+            count_unbiased += unbiased(&mut rng, n);
+        }
+
+        let b_percentage = 100.0 * count_biased as f64 / SAMPLES as f64;
+        let ub_percentage = 100.0 * count_unbiased as f64 / SAMPLES as f64;
+        println!(
+            "bias {}:  {:0.2}%   {:0.2}%",
+            n, b_percentage, ub_percentage
+        );
+    }
+}