September 2017 Update

Task/Subtractive-generator/Dc/subtractive-generator.dc

@@ -0,0 +1,52 @@
+[*
+ * (seed) lsx --
+ * Seeds the subtractive generator.
+ * Uses register R to hold the state.
+ *]sz
+[
+ [* Fill ring buffer R[0] to R[54]. *]sz
+ d 54:R SA              [A = R[54] = seed]sz
+ 1 d 33:R SB            [B = R[33] = 1]sz
+ 12 SC                  [C = index 12, into array R.]sz
+ [55 -]SI
+ [                      [Loop until C is 54:]sz
+  lA lB - d lC:R         [R[C] = A - B]sz
+  lB sA sB               [Parallel let A = B and B = A - B]sz
+  lC 34 + d 55 !>I d sC  [C += 34 (mod 55)]sz
+  54 !=L
+ ]d SL x
+ [* Point R[55] and R[56] into ring buffer. *]sz
+ 0 55:R                 [R[55] = index 0, of 55th last number.]sz
+ 31 56:R                [R[56] = index 31, of 24th last number.]sz
+ [* Stir ring buffer. *]sz
+ 165 [                  [Loop 165 times:]sz
+  55;R;R 56;R;R - 55;R:R [Discard a random number.]sz
+  55;R 1 + d 55 !>I 55:R [R[55] += 1 (mod 55)]sz
+  56;R 1 + d 55 !>I 56:R [R[56] += 1 (mod 55)]sz
+  1 - d 0 <L
+ ]d sL x
+ LAsz LBsz LCsz LIsz LLsz
+]ss
+
+[*
+ * lrx -- (random number from 0 to 10^9 - 1)
+ * Returns the next number from the subtractive generator.
+ * Uses register R, seeded by lsx.
+ *]sz
+[
+ 55;R;R 56;R;R -        [R[R[55]] - R[R[56]] is next random number.]sz
+ d 55;R:R               [Put it in R[R[55]]. Also leave it on stack.]sz
+ [55 -]SI
+ 55;R 1 + d 55 !>I 55:R [R[55] += 1 (mod 55)]sz
+ 56;R 1 + d 55 !>I 56:R [R[56] += 1 (mod 55)]sz
+ [1000000000 +]sI
+ 1000000000 % d 0 >I    [Random number = it (mod 10^9)]sz
+ LIsz
+]sr
+
+
+[* Seed with 292929 and print first three random numbers. *]sz
+292929 lsx
+lrx psz
+lrx psz
+lrx psz

Task/Subtractive-generator/Zkl/subtractive-generator-1.zkl

@@ -0,0 +1,12 @@
+fcn rand_sub(x){
+   var ring=L(),m=(1e9).toInt();
+   mod:='wrap(n){ if(n<0) n+m else n };
+   if(not ring){
+      seed:=L( (if(vm.numArgs) x else m-1), 1);
+      foreach n in ([2 .. 54]){ seed.append((seed[n-2]-seed[n-1]):mod(_)) }
+      foreach n in (55){ ring.append(seed[(34*(n+1))%55]) }
+      do(220-ring.len()){ self.fcn() } // 165
+   }
+   ring.append((ring.pop(0)-ring[-24]):mod(_));
+   return(ring[-1]);
+}

Task/Subtractive-generator/Zkl/subtractive-generator-2.zkl

@@ -0,0 +1 @@
+do(4){ println(rand_sub(292929)) } //seed ignored after first call