[TUHS] Lorinda Cherry
leah at vuxu.org
Thu Feb 17 00:54:16 AEST 2022
markus schnalke <meillo at marmaro.de> writes:
> [2022-02-16 00:54] arnold at skeeve.com
>> Dave Horsfall <dave at horsfall.org> wrote:
>> > You know you're a greybeard if you can remember why the DC sequence
>> > "99k2vp8opq" was so popular...
>> > -- Dave
>> I guess I'm not enough of a greybeard:
>> $ dc
>> I recognize the first value as the square root of two. What is
>> the second value?
> Decoding the program with the manpage:
> 99k set scaling factor to 99 (i.e. 99 digits on output)
> 2v square root of 2
> p print it (but leave it on the stack)
> 8o switch to octal output
> p print the same value (now in octal)
> q quit
> More interesting is the question why you need sqrt(2) in octal?
Apparently it was a popular benchmark back in the day:
> Tim Long: Quick Benchmarks of the Machines on Display
> A simple cpu-bound benchmark was run on each of the machines on display.
> The benchmark was "echo 99k2vp8opq I /bin/time dc > /dev/null’. It uses dc
> (the desk calculator) to calculate the square root of 2 to 99 decimal places,
> and to "print" the result in decimal and then in octal. The results are in
> fact never printed, being piped to /dev/null. The user time is all that is
> This benchmark has been applied to a large number of machines° It has
> (up until now) been useful because most manufacturers have not optimised dc,
> so the results are not likely to have been distorted by attempts to optimise
> for benchmarks.
> The results were:
> DoEo UNITY (DE-68K) 11.3 sec
> Plexus P/25 14.1 sec
> NCR Tower 21.3 sec
> Wicat 150WS 27.3 sec
> Unison 32.6 sec
> By comparison, a VAX 11/780 clocks about 5 to 6 secs, VAX750 9 sec, PDPIIs
> range from 27 secs (11/23) to 6 secs (11/70), PDP ii/34s range from 12 to 19
> secs depending upon the presence of a cache. Perkin-Elmer range from 12o5
> secs (32/10) to 7°9 secs (32/40)o
I looks like V7 dc used 100-limbs internally, so printing in decimal
was fast, but printing in octal required conversion.
Leah Neukirchen <leah at vuxu.org> https://leahneukirchen.org/
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