Project Update

[Dingo]

I have crunched enough work now to Create the Team.  Join BOINC-AUSTRALIA if you run this non BOINC project.


Keep it running

On Linux, running the client as a systemd service keeps it running across reboots. Create a unit file at /etc/systemd/system/crunch.service:

[Unit]
Description=primecrunch client
After=network-online.target
Wants=network-online.target

[Service]
ExecStart=/path/to/crunch  ## CHANGE THIS
Restart=on-failure
User=yourlinuxusername  ## CHANGE THIS

[Install]
WantedBy=multi-user.target


Then enable and start it:

sudo systemctl enable --now crunch

[Dingo]

Instead of making it a service I found that putting an entry in the crontab.

process in a linux terminal

1. sudo crontab -e  # Note here r is next to e on the keyboard and if you press r instad of e (contab -r) it deletes the crontab which is not good.

2. put this entry after all the commented out section.

@reboot /PATH/TO/crunch -p 4 >/var/log/crunch.log 2>&1 & 
>/var/log/crunch.log 2>&1 & 
##  EG MINE IS  @reboot /root/PrimeCrunch/crunch -p 4 >/var/log/crunch.log 2>&1 & 

NOTE: The -p lets you assign how many Threads to use.  If left off it will use all Threads.
NOTE:  If you forget the & cron will hang until crunch exits — which it never does.

That's it when you reboot or start the machine it will start crunch

If you use this and you want to stop the job from running use this command.

# Stop PrimeCrunch
pkill -f "/PATH/TO/crunch" 2>/dev/null

eg  mine is

pkill -f "/root/PrimeCrunch/crunch" 2>/dev/null


Added the Windows start crunch at machine start

1. Find the crunch program on your computer.

2. Create a shortcut and if you want to restrict the number of cores used in the Target block enter -p [number of cores] after crunch.
eg mine is "C:\Users\giles\PrimeCrunch\crunch.exe -p4"

3.Press the Windows key + R key to open the run box.

4. Paist shell:programs in the box and press enter.  The start menu window will open;

5. Open the StartUp folder and Paste your created shortcut into that folder.

6.  That's it, the first reboot or start you might get a warning asking if you really want to start this program.. If you trust it, well you are running it, click the box to deselect ask next time and press enter or whatever the button says can't remember.

7.  To stop crunch from starting at startup open the Task Manager and click the Startup Apps button. Right click on crunch and disable.  Do the opposite to enable it afterwards.

[Dingo]

New feature added after one of my enquiries.

I had this post:

I created two 4003 and 4005. Looking at the ones running now they are small digit blocks.

I have one machine that I would like to allocate longer jobs to. What K number would be one that is over a 2,000,000 digits. My largest prime found on Primegrid is 2,060,937 digits.

His reply was to create a new page where you can estimate.

https://primecrunch.com/digit-calculator?k=999&d=1000000

[Dingo]

Found a new page for Help and Documentation

Weaning myself off this project now that the Team is created but leaving  a couple of vps on it.

[Dingo]

I 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.

Dingo
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 Expand

#!/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.

[Dingo]

Text on the forum.

Separately, on formatting: you used

Code Select Expand

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.