September 2017 Update

Task/Percolation-Mean-cluster-density/Perl-6/percolation-mean-cluster-density.pl6

@@ -0,0 +1,66 @@
+my @perc;
+my $fill = 'x';
+
+enum Direction <DeadEnd Up Right Down Left>;
+
+my $𝘒 = perctest(15);
+.fmt("%-2s").say for @perc;
+say "𝘱 = 0.5, 𝘕 = 15, 𝘒 = $𝘒\n";
+
+my $trials = 5;
+for 10, 30, 100, 300, 1000 -> $𝘕 {
+    my $𝘒 = ( [+] perctest($𝘕) xx $trials ) / $trials;
+    say "𝘱 = 0.5, trials = $trials, 𝘕 = $𝘕, 𝘒 = $𝘒";
+}
+
+sub infix:<deq> ( $a, $b ) { $a.defined && ($a eq $b) }
+
+sub perctest ( $grid ) {
+    generate $grid;
+    my $block = 1;
+    for ^$grid X ^$grid -> ($y, $x) {
+        fill( [$x, $y], $block++ ) if @perc[$y; $x] eq $fill
+    }
+    ($block - 1) / $grid²;
+}
+
+sub generate ( $grid ) {
+    @perc = ();
+    @perc.push: [ ( rand < .5 ?? '.' !! $fill ) xx $grid ] for ^$grid;
+}
+
+sub fill ( @cur, $block ) {
+    @perc[@cur[1]; @cur[0]] = $block;
+    my @stack;
+    my $current = @cur;
+
+    loop {
+        if my $dir = direction( $current ) {
+            @stack.push: $current;
+            $current = move $dir, $current, $block
+        }
+        else {
+            return unless @stack;
+            $current = @stack.pop
+        }
+    }
+
+    sub direction( [$x, $y] ) {
+        ( Down  if @perc[$y + 1][$x] deq $fill ) ||
+        ( Left  if @perc[$y][$x - 1] deq $fill ) ||
+        ( Right if @perc[$y][$x + 1] deq $fill ) ||
+        ( Up    if @perc[$y - 1][$x] deq $fill ) ||
+        DeadEnd
+    }
+
+    sub move ( $dir, @cur, $block ) {
+        my ( $x, $y ) = @cur;
+        given $dir {
+            when Up    { @perc[--$y; $x] = $block }
+            when Down  { @perc[++$y; $x] = $block }
+            when Left  { @perc[$y; --$x] = $block }
+            when Right { @perc[$y; ++$x] = $block }
+        }
+        [$x, $y]
+    }
+}

Task/Percolation-Mean-cluster-density/Zkl/percolation-mean-cluster-density-1.zkl

@@ -0,0 +1,29 @@
+const X=-1;	// the sentinal that marks an untouched cell
+var C,N,NN,P;
+fcn createC(n,p){
+   N,P=n,p; NN=N*N;
+   C=NN.pump(List.createLong(NN),0);  // vector of ints
+   foreach n in (NN){ C[n]=X*(Float.random(1)<=P) } // X is the sentinal
+}
+fcn showCluster{
+   alpha:="-ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz";
+   foreach n in ([0..NN,N]){ C[n,N].pump(String,alpha.get).println() }
+}
+fcn countClusters{
+   clusters:=0;
+   foreach n in (NN){
+      if(X!=C[n]) continue;
+      fcn(n,v){
+	 if((0<=n<NN) and C[n]==X){
+	    C[n]=v;
+	    self.fcn(n-N,v); self.fcn(n-1,v); self.fcn(n+1,v); self.fcn(n+N,v);
+	 }
+      }(n,clusters+=1);
+   }
+   clusters
+}
+fcn tests(N,n,p){
+   k:=0.0;
+   foreach z in (n){ createC(N,p); k+=countClusters().toFloat()/NN; }
+   k/n
+}

Task/Percolation-Mean-cluster-density/Zkl/percolation-mean-cluster-density-2.zkl

@@ -0,0 +1,6 @@
+createC(15,0.5);
+println("width=%d, p=%.1f, %d clusters:".fmt(N,P,countClusters()));
+showCluster();
+
+println("p=0.5, 5 iterations:");
+w:=4; do(6){ println("%5d %9.6f".fmt(w,tests(w, 5, 0.5))); w*=4; }