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#6
Prime Crunch / Re: Project Update
Last post by Dingo - July 26, 2026, 08:16:28 PMText on the forum.
Separately, on formatting: you used
Separately, on formatting: you used
Code Select
and [quote] in your first post and they came out literally. That's on me for never documenting what the composer accepts. It takes markdown, not BBCode.
The composer has two tabs, Rich text and Markup. Rich text gives you a toolbar with Inline code (Ctrl/Cmd+E) and Code block buttons. Markup is the raw source if you'd rather type it directly.
The markup, written out literally:
`code` between single backticks
**bold** *italic* ~~strike~~
> a quoted line
- a bullet
1. a numbered item
[text](https://example.com) a link
@[name] mentions someone
:smile: emoji
For a code block, put three backticks on a line of their own above and below the text.
No headings or images on the forum, those are blog only. #7
WORD LINK / Re: Word Link 2
Last post by Dingo - July 26, 2026, 06:22:35 PMBogan ~ I was posted there to 221 Supply Company an Ammunition depot from Apr 79 to Dec 82. It has been closed down now for a long long time. There is still just a school, Pub. and a local shop and under 300 houses.
#8
Prime Crunch / Re: Project Update
Last post by Dingo - July 26, 2026, 06:15:36 PMI have been working with Andy the person behind the project to see if he will create a RPI Linux 64 version of the application.
prst The client is really just a wrapper. The actual maths is done by prst, which is built on gwnum, George Woltman's FFT library from Prime95. gwnum is hand written x86-64 assembly with separate code paths for SSE2, AVX2 and AVX-512. There is no ARM64 build of it, and porting it means rewriting the assembly core. That's a serious project in its own right and not something I can take on.
So there are two possible routes:
Emulation. Box64 on 64 bit Raspberry Pi OS. That's the one you can try today without me doing anything. I have no numbers for it. My expectation is that it will be poor, because gwnum's speed comes almost entirely from wide SIMD, and translating AVX2 onto a Cortex-A72 with 128 bit NEON is close to the worst case for a translator. But I would rather see a measurement than a guess. If you fancy trying it, grab the linux x86_64 client, run it under box64 and post how long a single Fermat test takes.
Swap gwnum for a generic bignum library like GMP. That would be native and would run anywhere, but the maths is the whole game here. gwnum uses an irrational base DWT, which is why a test at n = 1.5M takes minutes. A generic modpow at that size is orders of magnitude slower. You would get a native arm64 client that still reports almost nothing.
Even assuming a perfect hypothetical ARM64 port, the hardware gap is big. An A72 core does 2 doubles per FMA at 1.5GHz, a modern x86 core does 4 or 8 per FMA at over 4GHz, so roughly 10x per core before you account for anything else. These FFTs are also memory bandwidth hungry, and that is where the Pi 4 is weakest, with a few GB/s shared across all four cores. Your 16 Pis would land at a handful of modern desktop cores at best, and probably well under that.
So given that challenge and a bunch of testing and help from adam I finally got one of my RPI to complete a job.
I posted this on the forum at the project.
I am going to do the large one that is a known prime (1,415,549 digits) on one core of an RPI 4. I wrote a little script so I didn't have to wait and watch as it is going to be along time. maybe 12 hours I don't have a clue really.
I am hoping that andy will be able to make a wrapper for a ARM64 client if this finishes and it gives the correct answer.
prst The client is really just a wrapper. The actual maths is done by prst, which is built on gwnum, George Woltman's FFT library from Prime95. gwnum is hand written x86-64 assembly with separate code paths for SSE2, AVX2 and AVX-512. There is no ARM64 build of it, and porting it means rewriting the assembly core. That's a serious project in its own right and not something I can take on.
So there are two possible routes:
Emulation. Box64 on 64 bit Raspberry Pi OS. That's the one you can try today without me doing anything. I have no numbers for it. My expectation is that it will be poor, because gwnum's speed comes almost entirely from wide SIMD, and translating AVX2 onto a Cortex-A72 with 128 bit NEON is close to the worst case for a translator. But I would rather see a measurement than a guess. If you fancy trying it, grab the linux x86_64 client, run it under box64 and post how long a single Fermat test takes.
Swap gwnum for a generic bignum library like GMP. That would be native and would run anywhere, but the maths is the whole game here. gwnum uses an irrational base DWT, which is why a test at n = 1.5M takes minutes. A generic modpow at that size is orders of magnitude slower. You would get a native arm64 client that still reports almost nothing.
Even assuming a perfect hypothetical ARM64 port, the hardware gap is big. An A72 core does 2 doubles per FMA at 1.5GHz, a modern x86 core does 4 or 8 per FMA at over 4GHz, so roughly 10x per core before you account for anything else. These FFTs are also memory bandwidth hungry, and that is where the Pi 4 is weakest, with a few GB/s shared across all four cores. Your 16 Pis would land at a handful of modern desktop cores at best, and probably well under that.
So given that challenge and a bunch of testing and help from adam I finally got one of my RPI to complete a job.
I posted this on the forum at the project.
QuoteDingo
3 hours ago
edited
It ran and didn't have any errors reported. The time is very close.
dingo@C1-Ubuntu:~/prst-folder$ BOX64_LOG=0 box64 ./prst "1005*2^100000-1" -cpu SSE2
[BOX64] Box64 arm64 v0.4.3 a2ae0500d with Dynarec built on Jul 25 2026 10:57:54
dingo@C1-Ubuntu:~/prst-folder$
cat result.txt
"1005*2^100000-1" is not a probable prime. Have you run Fermat test first? RES64: 16F98A5F08A1F731, time: 68 s.
I am going to try a bigger one that is a prime on my list.
dingo@C1-Ubuntu:~/prst-folder$ BOX64_LOG=0 box64 ./prst "4005*2^56366-1" -cpu SSE2
start time 15:07 AEST Finish time 16:27 AEST
Results
BOX64_LOG=0 box64 ./prst "4005*2^56366-1" -cpu SSE2
[BOX64] Box64 arm64 v0.4.3 a2ae0500d with Dynarec built on Jul 25 2026 10:57:54
"4005*2^56366-1" is prime! Time: 19.1 s.
cat result.txt
"4005*2^56366-1" is prime! Time: 19 s.
looking good.
I am going to do the large one that is a known prime (1,415,549 digits) on one core of an RPI 4. I wrote a little script so I didn't have to wait and watch as it is going to be along time. maybe 12 hours I don't have a clue really.
Code Select
#!/bin/bash
LOGFILE="/home/dingo/prst-folder/result.txt"
# Record start time
START_TIME=$(date +%s)
echo "Prime Search Start: $(date)" >> "$LOGFILE"
# Run your Box64 job
BOX64_LOG=0 box64 ./prst "1011*2^4702339-1" -cpu SSE2 >> "$LOGFILE"
# Record end time
END_TIME=$(date +%s)
RUNTIME=$((END_TIME - START_TIME))
# Summary
echo "Prime Search End: $(date)" >> "$LOGFILE"
echo "Total runtime: ${RUNTIME}s" >> "$LOGFILE"
echo "------------------------------------------------------------" >> "$LOGFILE"
Using one core:
16649 dingo 20 0 177984 109948 15156 R 99.7 2.8 0:12.30 prst
I am hoping that andy will be able to make a wrapper for a ARM64 client if this finishes and it gives the correct answer.
#10
YAFU / Re: Project Updates
Last post by Dingo - July 25, 2026, 09:54:38 PMQuote[YAFU] Aliquot sequence 2086050 has terminated!!![/url]
View article ยท Fri, 24 Jul 2026 05:42:10 +0000