note BrowserUk <blockquote><i></i></blockquote> <p>Perhaps you missed the significance of the timings:<code> C:\test>1011850 -O=100000 Dict read at C:\test\1011850.pl line 96. objects loaded at C:\test\1011850.pl line 106. App created at C:\test\1011850.pl line 112. Ovid: (optimal ordering) returned 9193 objs in 4.447958 seconds Ovid: (pessimal ordering) returned 9193 objs in 7.236690 seconds RichardK: (optimal ordering) returned 9193 objs in 4.065038 seconds RichardK: (pessimal ordering) returned 9193 objs in 6.219226 seconds BUK: returned 9193 objs in 0.760572 seconds Filters run at C:\test\1011850.pl line 138. </code> <p>Running your OP algorithm against a set of 100 filters each carefully arrange to filter an increasing number of objects and ordered best to worst, and running two tests -- optimal and pessimal -- the difference between then is less that 50%. That is the best you can hope to achieve with your order-the-filters mechanism. <p>However, by altering the way the filters operate upon the objects, you can achieve an order of magnitude saving. <p>Or perhaps you've just decided how you want to tackle the problem. Regardless... <div class="pmsig"><div class="pmsig-171588"> <hr /> <font size=1 > <div>With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'</div> <div>Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.</div> <div>"Science is about questioning the status quo. Questioning authority". </div> <div>In the absence of evidence, opinion is indistinguishable from prejudice. </div> </font> </div></div> 1011650 1012016