The number π calculation by spigot algorithm benchmark

The table below consists of the best results for the listed computers. It is open for the further expansion. So if anybody has faster implementation of spigot algorithm for one of systems listed below then please inform the author of this page (to vol.litwr at gmail dot com) and it should be updated. The same is true for the results of other systems missed in the table.

This algorithm speed depends very much on the speed of integer division. So systems with hardware division have a big advantage.

The results are time intervals in seconds for the calculation of 100, 1000, 3000 digits. They also contain the upper limits to the number of digits for programs used. The data are sorted by time for 3000 digits.

Every program is satisfying four restrictions: 1) it measures time; 2) it uses an OS function to print digits, it prints 4 digits a time synchronously with the calculation of them; 3) it uses less than 64 KB RAM for the code and data; 4) it utilizes all available RAM below 64 KB limit to get the maximum number of calculated digits, so it is forbidden to restrict artificially the maximum number of digits.

CPU frequencies given are maximum available (known to me) for computers listed below. They are actual frequencies used during measurements.

FORMAT: Data for CPU and IO timing parts are calculated, so they are only some approximations. They are less accurate for display outputs because timings for the vertical scrolling are not taken into account. They have also some small deviations (about 5%) for tcp/ip connections because of not linear timing for the char output in this case. For some systems, the data was acquired from hardware. Approximated results are shown in blue. The red color is used in cases where the approximation is based on heuristics.


1The automatic DRAM regeneration doesn't work at this clock (@1.78MHz) so it is possible that some hardware and software can't work with this speed. So, for normal system work, the maximum clock frequency is about 1.34 MHz, or 75% of that that used for the results given in the table.

The results above allow to calculate CPU efficiency for 1 Mhz. The next table contains approximate values of efficiency reciprocals (ER). These values are calculated by multiplication of the time (CPU time only without IO) of the calculation of 3000 digits by the CPU frequency. The ER values are gotten for pi-spigot which uses base 16-bit integer arithmetic. The best ER value for each CPU is taken. The ER value reflects the efficiency of a CPU electronics.

The next table contains details about the tested systems in the chronological order.


The next table contains the sizes of the main loops and the whole programs.
ProgramCPUMain loopTotal
vax-bsd-1VAX34816*4
vax-vms-2VAX34915*2
ibm370cms-1IBM/37036750
bbc-pandora-23201637992
bbc-panos-232016371044
msdos-5808654635—640
ibmpc-7808654654
atarist30-96803054724
amiga1200-136802054812
atarist-96800056730
amiga-136800056816
pc386-88038657624
geneve-mdos-1TMS9900621001*2
ti99-4a-2eaTMS990062520+626=1146*1
dragon-6309-4630997281+496=777*1
pdp11-unix7-eis-1PDP-11/EIS170636*4
rt11-eis-12ofPDP-11/EIS170869*2
dragon-66809303810+484=1294*1
arm2-1ARM25161504
arm1-4ARM15401680
bk11-7PDP-116461446
bk10-7PDP-116461446
pdp11-unix7-noeis-1PDP-117341258*4
rt11-noeis-7PDP-117341476*2
scpu64-765816250+768=1018*5[1764+228+2]=1994*7
apple2gs-165816250+768=1018*51906+416=2322*1
bbc-z80-3Z80748+768=1516*51792+292=2084*1
msx-3Z80748+768=1516*51799+460=2265*1
cpm22bios-7Z80748+768=1516*52270—2283
trsdos-m1-1Z80748+768=1516*52284
trsdos-m3-1Z80748+768=1516*52286
cpc-cpm3-10Z80748+768=1516*52287
trsdos-m4-1Z80748+768=1516*52299
cpc-5Z80748+768=1516*51804+579=2383*1
cpm22bdos-7Z80748+768=1516*52266—2548
zx-1Z80748+768=1516*54666*3
abc800-1Z80748+768=1516*51804+579=4684*8
tandy100-18085992+768=1760*52054+378=2432*1
cpm22bios-8080-280801285+768=2053*52804
vic20-365022353+768=3121*5*6[3497+264+2]=3773*7
plus4-1365022353+768=3121*5*6[3501+526+2]=4029*7
c64-1365022353+768=3121*5*6[3668+359+2]=4029*7
c128-1265022353+768=3121*5*6[3668+359+2]=4029*7
bbc-865022353+768=3121*5*6[3484]+461+[177]=4122*7
apple2e-265022353+768=3121*5*63731+437=4168*1
atari800xl-665022353+768=3121*5*63515+[1291+177]=4983*7
apple2c-65c02-265C022866+768=3634*5*64234+432=4666*1
*1 it is a sum of Asssember + Basic code sizes.
*2 it is a size of the pure code without a header
*3 it is a size of the TAP-file
*4 it is a size of the assembler + C code without a loader and C-libraries
*5 code size + the size of multiplication lookup table
*6 the 6502 code may be shorter (1871+768=2639) – this makes it 1-2% slower
*7 it is a sum of Asssember + Basic + header/loader code sizes.
*8 it is a size of Basic text that contains embedded ML-code.

Thanks a lot for people who helped: bqt, ivagor, perestoronin, BigEd, tricky, MMS, Thorham, meynaf, ...


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