11 September 2009

This week I learned...

It's prehistory week at the jorendorff household. This week I learned:

  • The fossilized skeletons of a 14-foot Xiphactinus (a mean-looking Late Cretaceous fish) and its last meal, a merely 6-foot bony fish which it swallowed whole, are on display at the Sternberg Museum of Natural History in Hays, Kansas.

  • Woolly mammoths had a three-inch-thick layer of fat underneath thick skin, fur, and long shaggy hair. (Yet their environment was such that occasionally one would be flash-frozen, without spoiling the meat, to be eaten by modern dogs ten thousand years later.)

Last week:

  • The original Nintendo GameBoy had an 8-bit processor with a HALT instruction which games were supposed to use to wait for interrupts. At least one game would sometimes busy-wait instead (yuck!).

  • There's a tool, dwarfdump, that dumps DWARF debug info from an executable or object file.

  • On Mac there's a lazy debug-info-linking scheme that causes dwarfdump not to see any DWARF in compiled executables. The Mac tools that come with Xcode are aware of this magic, but dwarfdump isn't.

Earlier still:

  • The Spiral of Theodorus shows that the square roots of integers can be constructed with straight edge and compass.

  • According to Tim Sweeney, quoted in this DDJ article:

    Any loop written in a traditional programming language can be vectorized, to execute 16 iterations of the loop in parallel on Larrabee vector units, provided the loop body meets the following criteria:

    • Its call graph is statically known.
    • There are no data dependencies between iterations.

    So compilers will be able to do a lot more vectorization.


Ted Mielczarek said...

I guess that's why my old gameboy got such great battery life. 4 AA batteries would last forever.

Benjamin Smedberg said...

I didn't know about the Spiral of Theodorus. I'm excited!