$i = 1 + $hash % ($p-1)

my $j = ( 1 + $i ) % ( 17 - 1 );

I'm not sure who you got those extra parens from, but they weren't from me. :)

Or, looking at it another way:

my $i=0;

The point of my suggestion, $i = 1 + $hash % ($p-1), is that it never results in $i == 0 (even if your computed $hash equals 0). So calling out the line that resulted from you doing $i=0 doesn't really have much bearing on the validity of my suggestion.

Does any of that help you see how you misinterpreted my suggestion? I ask because I'm not completely sure were the disconnect is and I'm reluctant to try guess at what I should try to explain.

You're right! I misread the precedence. Is this what you meant?

for( my $i=0; $i<17; ++$i ) { 
    my $j =  1 + ( $i % ( 17 - 1 ) ); 
    printf "%2u: %s\n", $i, join' ', map{ sprintf "%2u", $j = ( $j + $
+i ) % 17 } 0 .. 16; 
};;
 0:  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 1:  3  4  5  6  7  8  9 10 11 12 13 14 15 16  0  1  2
 2:  5  7  9 11 13 15  0  2  4  6  8 10 12 14 16  1  3
 3:  7 10 13 16  2  5  8 11 14  0  3  6  9 12 15  1  4
 4:  9 13  0  4  8 12 16  3  7 11 15  2  6 10 14  1  5
 5: 11 16  4  9 14  2  7 12  0  5 10 15  3  8 13  1  6
 6: 13  2  8 14  3  9 15  4 10 16  5 11  0  6 12  1  7
 7: 15  5 12  2  9 16  6 13  3 10  0  7 14  4 11  1  8
 8:  0  8 16  7 15  6 14  5 13  4 12  3 11  2 10  1  9
 9:  2 11  3 12  4 13  5 14  6 15  7 16  8  0  9  1 10
10:  4 14  7  0 10  3 13  6 16  9  2 12  5 15  8  1 11
11:  6  0 11  5 16 10  4 15  9  3 14  8  2 13  7  1 12
12:  8  3 15 10  5  0 12  7  2 14  9  4 16 11  6  1 13
13: 10  6  2 15 11  7  3 16 12  8  4  0 13  9  5  1 14
14: 12  9  6  3  0 14 11  8  5  2 16 13 10  7  4  1 15
15: 14 12 10  8  6  4  2  0 15 13 11  9  7  5  3  1 16
16:  0 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1
[download]

0 % anything == 0 so i becomes 1 + 0; and 0 gets added at each iteration; which never terminates.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this

In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

I guess you need to have your demonstration code take a step back so that it is closer to the actual hashing problem in order for you to be able to use it to demonstrate the value of my suggestion. For example:

my $p = 17;
for my $hash ( 0 .. 20 ) {
    my $i = 1 + $hash % ($p-1);
    my $j = $i;
    printf "%2u: %2u %s\n", $hash, $i, join ' ', map { sprintf "%2u", 
+$j = ( $j + $i ) % $p } 0 .. 16;
}
__END__
hash 1st
  0:  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16  0  1
  1:  2  4  6  8 10 12 14 16  1  3  5  7  9 11 13 15  0  2
  2:  3  6  9 12 15  1  4  7 10 13 16  2  5  8 11 14  0  3
  3:  4  8 12 16  3  7 11 15  2  6 10 14  1  5  9 13  0  4
  4:  5 10 15  3  8 13  1  6 11 16  4  9 14  2  7 12  0  5
  5:  6 12  1  7 13  2  8 14  3  9 15  4 10 16  5 11  0  6
  6:  7 14  4 11  1  8 15  5 12  2  9 16  6 13  3 10  0  7
  7:  8 16  7 15  6 14  5 13  4 12  3 11  2 10  1  9  0  8
  8:  9  1 10  2 11  3 12  4 13  5 14  6 15  7 16  8  0  9
  9: 10  3 13  6 16  9  2 12  5 15  8  1 11  4 14  7  0 10
 10: 11  5 16 10  4 15  9  3 14  8  2 13  7  1 12  6  0 11
 11: 12  7  2 14  9  4 16 11  6  1 13  8  3 15 10  5  0 12
 12: 13  9  5  1 14 10  6  2 15 11  7  3 16 12  8  4  0 13
 13: 14 11  8  5  2 16 13 10  7  4  1 15 12  9  6  3  0 14
 14: 15 13 11  9  7  5  3  1 16 14 12 10  8  6  4  2  0 15
 15: 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0 16
 16:  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16  0  1
 17:  2  4  6  8 10 12 14 16  1  3  5  7  9 11 13 15  0  2
 18:  3  6  9 12 15  1  4  7 10 13 16  2  5  8 11 14  0  3
 19:  4  8 12 16  3  7 11 15  2  6 10 14  1  5  9 13  0  4
 20:  5 10 15  3  8 13  1  6 11 16  4  9 14  2  7 12  0  5
[download]

An interesting side-effect is that slot 0 is now always the last slot to be filled (I believe).

- tye