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Think about Loose Coupling

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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 ''; }

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The start of some sanity?

In reply to Re^7: [OT] The statistics of hashing. (odd) by BrowserUk
in thread [OT] The statistics of hashing. by BrowserUk

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