Wednesday, May 30, 2007

powers of two

Knuth Check
Originally uploaded by dyoo
One of my friends complained that I didn't put any interesting images on my blog. So I promised him I'd post something with an image on it. I thought this photo would bring a smile to his face.

Gotta love powers of two.


Unknown said...

You have to say what the fix you found was.

Danny Yoo said...

The bug was Knuth's translation of "Hello World" into MMIX opcodes in Fascicle 1 of TAOCP.

For fun, I had written a disassembler for MMIX and hand-compared the opcodes in the book versus the ones from the disassembled binary. To my great surprise, a few of the opcodes didn't match up!

Knuth explained that the opcodes had changed in some revision, and that he had forgotten to update the book example appropriately.