From: "Paul Gilmartin" <[email protected]>
Sent: Tuesday, 3 August 2010 12:06 AM
On Aug 2, 2010, at 07:49, john gilmore wrote:
The question--What use are one-bit counts for a bit string?--
would occur only to someone who was unfamiliar with bit
maps and their uses.
It was a machine instruction on the CDC 6600. Extremely fast;
and the Cyber 70 series. IIRC it was called a Population Count instruction.
likely piggybacked on a Wallace tree used for multiplication.
Even earlier, that used on DEUCE (c. 1960) made use of the asynchronous
multiplier to perform an automatic shift as part of the process.
To sum the 1-bits in a 32-bit word took 6 instructions
(including setup).
That's a far cry from the ~100 instructions required on the S/360 etc.
In likely consequence it became a BIF in Pascal.
