Glorious CCCG thread -- Cellphone Compute Cluster for GIMPS
 

I checked the Hadware subforum going back over 5 years and found no existing thread on this "idea which won't go away" which IMO is deserving of a dedicated thread. Couple of scene-setting articles:

o From 2010: [url=www.linux-mag.com/id/7845/]A Cluster In Your Pocket[/url] | Linux Magazine

o From 2015: [url=https://www.hpcwire.com/2015/01/27/new-purpose-old-smartphones-cluster-computing/]A New Purpose for Old Smartphones: Cluster Computing[/url] | HPCWire.com

I checked Wikipedia for more recent info re. the [url=https://en.wikipedia.org/wiki/PuzzlePhone]PuzzlePhone[/url] described in the HPCWire piece - it says " As of May 2017, the project is delayed indefinitely due to lack of funds."

A compute cluster made of repurposed Smartphone processor nodes is attractive for GIMPS-style work because we don't need the nodes to be able to intercommunicate, just have each node work on its own assignment and have some barebones system-comms capability to be able to load software onto the nodes and manage their resulting compute assignments.

Now, some cost estimation: I'm going to use my little Odroid-C2 Linux micro-PC by way of example here, because it uses a kind of low-power multicore (4) ARM processor similar to those used in many smartphones. My C2 yields about 1/20th the compute throughput of my similar-vintage Intel Haswell quad, at less than 1/20th the TDP (< 5W) and with a simple small-heatsink passive-cooling solution, so the power-consumption side of things is fine. But the C2 costs ~$50, several times more per FLOP than the Haswell. What is needed is a per-node cost of around $10, and an accompanying clustering hardware framework which allows many (20 or more) such nodes to be compactly housed and which costs no more than the nodes it holds. Given how many still-working smartphones are discarded each year, obtaining large quantities of them very cheaply may be feasible, but even in that case work to repurpose them for compute-cluster use - reflash-with-common-OS, break-out-mainboard-and-slap-heatsink-on-CPU, physically-connect-to-cluster-power-and-IO-buses, that sort of thing - would require nontrivial work and expense. High time for our local experts in the various hardware and software aspects of the problem to start brainstorming!

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[b]Edit: Here is the current how-to for doing this:[/b]

(Advisory: folks who haven't followed the thread closely since it inception are encouraged to read it by way of backgrounding, before spending their time and money on used-phone-for-parts-style gear.)

o User M344587487, who has been leading the charge on proof-of-principle, has kindly put together several handy utility scripts - see [url=https://www.mersenneforum.org/showpost.php?p=507155&postcount=51]his post on that[/url];

o Here is M344587487's latest list of candidate hardware - if you want to help out in this effort but don't have time to mess around with rooting hardware and such, please consider donating a used phone of the no-longer-usable-as-phone-but-screen-still-mostly-works variety. Should you own such a one on this list, PM me for a printable mailing label you can use to ship it:

Or maybe linux based consumer/commodity wireless routers that can be reflashed.
Node to node communication is redundantly covered. [URL]https://en.wikipedia.org/wiki/Linksys_WRT54G_series[/URL]

I'm not convinced much more than bluetooth would be needed, for work and result communication, so lots of phones would be ok there as is. Might be a place to use those old small micro SD cards too. If you don't mind using some shelf or wall space, or aesthetics, perhaps temporarily, a 1x8 pine board could hold 20+ phones in a pinboard arrangement (similar to the tool used for building wire harnesses) using a box of finishing nails to hold and space the phones, and guide power leads. Reuse the microUSB tails from numerous failed chargers, and feed the array from a common power supply stationed near the center. How many amps would it need?

[QUOTE=ewmayer;505936]...
What is needed is a per-node cost of around $10, and an accompanying clustering hardware framework which allows many (20 or more) such nodes to be compactly housed and which costs no more than the nodes it holds. Given how many still-working smartphones are discarded each year, obtaining large quantities of them very cheaply may be feasible,
...[/QUOTE]
Ideally we're looking at Samsung S6 era at worst for efficiency. The S6 is getting bid beyond £30 with a broken screen, the S5 beyond £20, the iphone 6 is getting bid beyond £50 ensuring that's out of the running. You'd be hard pressed to find nodes cheap enough unless you have a good source or fancy buying phones sold as "dead" and going on an adventure.

[QUOTE=ewmayer;505936]...
but even in that case work to repurpose them for compute-cluster use - reflash-with-common-OS, break-out-mainboard-and-slap-heatsink-on-CPU,
...[/QUOTE]
Reflashing with Linux is probably only possible on some models due to manufacturer roadblocks and likely non-mainline-compatible hardware. Depends on how varied the 2nd hand phone market is, I'm seeing 90% Samsung phones when searching for android so maybe there's few enough models to deal with that it's viable. If that's out Android is the common OS and I'd likely go for that anyway, the only issue is getting it running if there's a fully dead screen. If you can root the phone you can run ELFs directly (I think) or alternatively it shouldn't be too hard to package Mlucas into an APK. With or without rooting you can install ssh/scp to send and receive work. The software steps to add a node would be factory reset, root if possible, remove bloatware, install ssh/scp and Mlucas ELF/APK, controller ssh's in to create worktodo, execute.

Hardware modding would be more of a pain. I'd remove the battery if possible, running full pelt 24/7 it's a fire waiting to happen (if the battery remains, at least let it discharge every few months). Slap a heatsink on, maybe even salvage what can be salvaged to get back some of the initial cost buying the node.

[QUOTE=ewmayer;505936]...physically-connect-to-cluster-power-and-IO-buses, that sort of thing - would require nontrivial work and expense. High time for our local experts in the various hardware and software aspects of the problem to start brainstorming![/QUOTE]
Luckily that's the easy bit. Android phones of that era all use micro USB which are around £0.50 each, which you connect to a powered USB hub. IO via wifi to a router which has a master computer sending/receiving work.

[QUOTE=kriesel;505938]...
How many amps would it need?[/QUOTE]
2A per node at 5V, the latest models we can't afford to use probably need 3A.

Hmm, so it sounds like at present, looking at a barebones cluster based on e.g. the RockPi4, as described in recent posts [url=https://mersenneforum.org/showthread.php?p=506060#post506060]here[/url], is a better bet. I guess it makes sense that there would be eager buyers for dead-screen phones, since if the guts of the phone still works, by definition it can be refurbished into a working phone. is there a "too broken to refurb-as-phone but still usable for crunching" niche, I wonder? Maybe we just need to find the right junkyard. :)

C64
 

I remember a similar discussion about porting Prime95 to a Commodore-64.
20 years ago there were more C-64s in people's basements than there were people on the planet.....well almost.

[QUOTE=ewmayer;506144]Hmm, so it sounds like at present, looking at a barebones cluster based on e.g. the RockPi4, as described in recent posts [URL="https://mersenneforum.org/showthread.php?p=506060#post506060"]here[/URL], is a better bet. I guess it makes sense that there would be eager buyers for dead-screen phones, since if the guts of the phone still works, by definition it can be refurbished into a working phone. is there a "too broken to refurb-as-phone but still usable for crunching" niche, I wonder? Maybe we just need to find the right junkyard. :)[/QUOTE]
"Wanted: ARM based smart phone, cheap.
Buyer's fine with dead battery, screen, keypad, and radio,
but it must have working processor, micro USB port, and ram."
Post in the usual places.

[QUOTE=kriesel;506153]"Wanted: ARM based smart phone, cheap.
Buyer's fine with dead battery, screen, keypad, and radio,
but it must have working processor, micro USB port, and ram."
Post in the usual places.[/QUOTE]

Seems like there should be piles of those available at the smart phone repair shops.

[QUOTE=PhilF;506154]Seems like there should be piles of those available at the smart phone repair shops.[/QUOTE]

That was more or less my druthers when I posted the thread ... don't own a smartphone myself, but next time one of you folks who does is at your local multibrand repair shop, by all means do ask!

(Actually, I think there is such a shop near me, but still fairly new to this town, need to pop in there next time I'm on the shop's street and see what kind of phone business they do.)

Some small business may be quite happy to have you take off their hands, what they may regard as the waste product of their revenue-generating activity, that takes time and money to dispose of. An uncle of mine gets free waste cooking oil from restaurants, which he converts to biodiesel fuel for his converted pickup truck. Otherwise they may have to pay someone to dispose of it.
You might want to have a 14-gallon tote in your vehicle; they may want their disposal bins back.

If that does not pan out, there are plenty of lots of varying quantities, for parts or repair, on ebay (some advertised as ~20 pounds). [URL]https://www.ebay.com/bhp/broken-cell-phone-lot[/URL]

Does anyone have any idea if an old Nokia 5165 would be of any use at all?

Motorola QA30?

[QUOTE=kriesel;506153]"Wanted: ARM based smart phone, cheap.
Buyer's fine with dead battery, screen, keypad, and radio,
but it must have working processor, micro USB port, and ram."[/QUOTE]You missed some important things:
Must also have a working Flash-ROM and be able to be rooted/re-flashed.

Without that last part you've got nothing workable.

[QUOTE=retina;506220]You missed some important things:
Must also have a working Flash-ROM and be able to be rooted/re-flashed.

Without that last part you've got nothing workable.[/QUOTE]
Also, phones, plural, preferably same model, ARM processor.