I accept your instinct on this as sufficiently authoritative to take at face value. Only you know what is really going on during the first phase scan.

What you've revealed in this thread strongly suggests it's reordering data, not merely reading it. My adaptation of your bitmap idea for use as a run-length indicator admitted popped into my head whilst I was presuming Phase I was simply a linear read operation.

It's still a fun problem, but I'm hard pressed to find anything else that might be optimized in Phase II based on metadata collected during Phase I.

I have no doubts you are taking into consideration all the conventional optimizations -- not that peer review hurts, even for the experienced, but that isn't the question you asked here. :-)

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.