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Re: Iterating over Blocks of 2-Dim Array

by punchcard_don (Beadle)
on Apr 01, 2004 at 13:20 UTC ( #341610=note: print w/ replies, xml ) Need Help??

in reply to Iterating over Blocks of 2-Dim Array

For the general case of an n x m matrix:
(note n & m evenly divisible by i & j respectively)

$rows = n; $cols = m; $rowstep = i; $colstep = j; $num_row_subs = $rows/$rowstep; $num_col_subs = $cols/$colstep; for $r (0 .. $num_row_subs-1) { for $c (0 .. $num_col_subs-1) { for $sub_row (0 .. $rowstep-1) { for $sub_col (0 .. $colstep-1) { $row = $r*$rowstep+$sub_row; $col = $c*$colstep+$sub_col; print "[$r*$rowstep+$sub_row = $row][$c*$colstep+$sub_ +col = $col]<br>\n"; } } } }
Switching order of for-loops changes manner of walking through sub-matrices.

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