I suspect you need to start $toggle reversed for odd values
Indeed. Using my $toggle = $P & 1 ? 1 : -1;, the output makes much more sense:
you don't show most of the code so I didn't go much further in looking
The entire code looks like this: #! perl -slw
use strict;
sub PTn {
my @row;
for( 1 .. shift ) {
push @row, 1;
$row [$_] += $row [$_ - 1] for reverse 1 .. @row - 2;
}
return @row;
}
sub expN {
my( $P, $N, $X ) = @_;
my $xDIVn = $X / $N;
my @coefs = PTn( $P+1 );
my $rv = 0;
my $toggle = $P & 1 ? 1 : -1;
for my $p ( reverse 1 .. $P ) {
$rv += $toggle * $coefs[ $p ] * $N / $p * exp( -$p * $xDIVn );
$toggle *= -1;
}
return $rv + $X;
}
our $H //= 10;
our $B //= 32;
print "Using N x 2**$B vectors:";
for my $inserts ( map{ 2**$_*3/4, 2**$_ } 4 .. $B ) {
printf "%10d : ", $inserts;
for my $h ( 1 .. $H ) {
printf "%6d ", expN( $h, 2**$B, $inserts ) - expN( $h, 2**$B,
+0 );
}
print '';
}
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".
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