note BrowserUk <blockquote><i>Rerunning with 5.16 yielded a runtime of 60 seconds.</i></blockquote> <p>Conclusion: With 384GB of ram; your (relatively) tiny 10e6 lines test file is being read from system file cache, hence effectively disguising the disk IO costs. <p>If your 80GB file fits in cache and will always be there when you need to do this; you can ignore the effects of disk. <P>Otherwise ... you need to re-run all your testing using the real file and having flushed the cache before each test. <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> 1014517 1015056