perlquestion orange hi <br/> ulam spiral is the prime numbers spiral, you can find info how to draw it in: <br/> [wp://Ulam_spiral] <br/> <p>each white dot represent a prime number. in the result we will see that the primes have some limited patterns. the following code draw the spiral (a square spiral), <code> #!/usr/local/bin/perl use strict; use Tk; my (\$order,\$pntcycle,\$pnts,\$b,\$num,\$p) = (0); my \$lastnumber; my \$NumOfPrimes=0; my (\$i, \$colr, \$counter); my(\$o, \$s) = (250, 20); my(\$pi, \$x, \$y) = (3.1415926, 0, 0); print "type the maximum number for the prime spiral \n"; my \$lastnumber = <>; print "please wait \n"; my \$mw = MainWindow->new; my \$c = \$mw->Canvas(-width => 500, -height => 500); \$c->pack; \$c->createLine(50, 250, 450, 250); \$c->createText(10, 250, -fill => 'blue', -text => 'X'); \$c->createLine(250, 50, 250, 450); \$c->createText(250, 10, -fill => 'blue', -text => 'Y'); OUTER: for (\$i= 1; \$i <= 250; \$i += 1) { \$order=\$order+1; if (\$order == 5){\$order = 1;} \$pntcycle = \$pntcycle + 1; if (\$pntcycle == 3) {\$pntcycle = 1; \$pnts = \$pnts + 1;} \$counter=0; while (\$counter <= \$pnts ) { \$counter++; \$num = \$num + 1; if (\$num == \$lastnumber+1) {last OUTER;} &is_prime(); if (\$b != 0) {\$colr = "white"; \$NumOfPrimes = \$NumOfPrimes + 1;} if (\$b == 0) {\$colr = "black";} if (\$order == 1) {\$x = \$x + 1;} elsif (\$order == 2) {\$y = \$y - 1;} elsif (\$order == 3) {\$x = \$x - 1; } elsif (\$order == 4) {\$y = \$y + 1; } \$c->createText( \$x+\$o, \$y+\$o, -fill => "\$colr", -text => '.'); } } MainLoop; sub is_prime { \$p=0; \$b=0; my \$j=0; my @prime_; for(\$j=1; \$j <= \$num; \$j++) { if(\$num % \$j==0) { \$prime_[\$p] = "\$j"; \$p++; } if (\$prime_ == \$num) { \$b = 1; } } } </code> but i have two problems, it is very slow, in my celeron 2 Ghz i draw the points up to 5000 in about 20 seconds. the algorithm for the checking the primality of numbers i have copied it from somewhere in this forum with a small variation. <br/> the other problem is that the final plot appear after the calculation have finished, i can't see the process of drawing dot by dot. <br/> <p>for comparison here is a visual basic 6 code and an executable file to demonstrate the defference: <br/> http://mihd.net/z58lv6 <br/> i am using ActivePerl-5.8.8.817-MSWin32-x86 <br/> windows xp