Parallel Computation
Another common optimization uses a lookup table indexed by highest order coefficients of rem to perform the inner loop over 8 bits in fewer steps. A 256-entry lookup table is a particularly common choice, although using a 16-entry table twice per byte is very compact and still faster than the bit at a time version. This replaces the inner loop over j with
- Code fragment 6: Cores of table based division
One of the most commonly encountered CRC algorithms is known as CRC-32, used by (among others) Ethernet, FDDI, ZIP and other archive formats, and PNG image format. Its polynomial can be written msbit-first as 0x04C11DB7, or lsbit-first as 0xEDB88320. The W3C webpage on PNG includes an appendix with a short and simple table-driven implementation in C of CRC-32. You will note that the code corresponds to the lsbit-first byte-at-a-time pseudocode presented here, and the table is generated using the bit-at-a-time code.
Read more about this topic: Computation Of CRC
Famous quotes containing the words parallel and/or computation:
“If from the earth we came, it was an earth
That bore us as a part of all the things
It breeds and that was lewder than it is.
Our nature is her nature. Hence it comes,
Since by our nature we grow old, earth grows
The same. We parallel the mother’s death.”
—Wallace Stevens (1879–1955)
“I suppose that Paderewski can play superbly, if not quite at his best, while his thoughts wander to the other end of the world, or possibly busy themselves with a computation of the receipts as he gazes out across the auditorium. I know a great actor, a master technician, can let his thoughts play truant from the scene ...”
—Minnie Maddern Fiske (1865–1932)