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Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

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Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#31

Post by willis936 »

WJW wrote: post #29
willis936 wrote: post #25

Earlier quoted context omitted.

1 is considered prime by some.

There are also people who consider the world to be flat though. There is a very thorough mathematical definition of prime numbers and 1 is not prime according to that definition.

The definition a prime number is having two factors. As the multiplicative identity, one only has one factor. Some might see primes as being numbers with >=2 factors. This interpretation is less useful. What is completely useless is a definition that makes exclusions of specific numbers as dogma. What does that say about anything? It’s totally arbitrary and unexplanatory.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#32

Post by smallpipe »

This is fun and all, but the benchmarks here aren't really what the author seems to think they are. This isn't "computationally expensive", the script is basically only control flow, where the CPU spend more time doing variable lookups than the actual computation. This means most of the pipeline width sits completely unused, whcih is a pretty large disservice to the M1 and the i5.

There's also no control for the thermal throttling of the M1, which is probably why the 100,000 example is performing worse.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#33

Post by willis936 »

rcxdude wrote: post #30
willis936 wrote: post #28

Earlier quoted context omitted.

That is not true. The energy efficiency will go down if you downclock because the static to dynamic power ratio will increase.

static to dynamic power ratio isn't efficiency though (and static power in modern desktop chips is tiny compared to the dynamic power). The dynamic power is not linearly related to processing speed (in fact it's much worse). If you downclock and undervolt a ryzen processor it will use much less power than the decrease in speed (e.g. from stock, if you drop performance by ~20% you might get a ~40% power decrease). Obv…

That scaling has a limited range before static power becomes dominant. Compute efficiency is compute / energy (total power * time). Total power includes static power. An SBC pulls far less from the wall than an x86 desktop could ever hope to when calculating the first million digits of pi.

As an example: even if I halted my desktop at 0 MHz and it still magically took the same time to calculate the first million digits of pi as a raspberry pi, it still would be using far more power.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#34

Post by thraway123412 »

wccrawford wrote: post #26
thraway123412 wrote: post #23

2GB Pi is $55 on amazon. 4GB version is $62. That'd be $450+ for the eight pies. Ryzen 2700 launched at $300 (and tapered down to ~$200) and would pretty much run circles around such a Pi cluster. Just saying. These Pi clusters can be a cool and fun thing to build but if you're looking for compute power, you'd be better served by a mid-range desktop.

Those 8 pis have all their hardware, though. The Ryzen needs all the rest of the hardware to finish off the computer.

Well, he also needed to add a cooler and a bunch of tubes & eight mounts to get coolant running on each Pi, eight ethernet cables, eight power cables, a power supply with enough outputs, a 16-port ethernet switch, and (correct me if I'm wrong) eight SD cards, if only to store a bootloader that can do pxe.

So eight Pies alone do not make a complete cluster, just as one Ryzen alone does not make a complete computer. A few times eight times cheap can turn out to be quite expensive, depending on how much cheap actually is.

I haven't paid much attention to component prices recently but my rule of thumb for budget builds is to start with $80 for each component that isn't a GPU or CPU. Go with stock cooler, grab 80 for PSU, 80 for mobo, 80 for RAM, 80 for storage, see where you end up. In the same ballpark, but the real computer will pack a whole lot more punch (even if you had less RAM total).

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#35

Post by spekcular »

willis936 wrote: post #31
WJW wrote: post #29

Earlier quoted context omitted.

There are also people who consider the world to be flat though. There is a very thorough mathematical definition of prime numbers and 1 is not prime according to that definition.

The definition a prime number is having two factors. As the multiplicative identity, one only has one factor. Some might see primes as being numbers with >=2 factors. This interpretation is less useful. What is completely useless is a definition that makes exclusions of specific numbers as dogma. What does that say about anything? It’s totally arbitrary and unexplanatory.

No, that is not the correct definition of a prime. You can find the right one on Wikipedia.

The reason that 1 is not a prime is to preserve unique factorization. A basic fact from number theory is that every integer uniquely factors as a product of primes, say 21 = 7 times 3. If 1 were a prime, we'd also have 21 = 7 times 3 times 1. That's bad.

In more general number rings, other units (e.g. i) are also not considered primes for the same reason. The exclusion is not arbitrary.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#36

Post by jamesbfb »

thraway123412 wrote: post #34
wccrawford wrote: post #26

Earlier quoted context omitted.

Those 8 pis have all their hardware, though. The Ryzen needs all the rest of the hardware to finish off the computer.

Well, he also needed to add a cooler and a bunch of tubes & eight mounts to get coolant running on each Pi, eight ethernet cables, eight power cables, a power supply with enough outputs, a 16-port ethernet switch, and (correct me if I'm wrong) eight SD cards, if only to store a bootloader that can do pxe. So eight Pies alone do not make a complete cluster, just as one Ryzen alone does not make a complete computer. A…

Jeff Geerling did a blog post[0] and video (series) on this very thing a while ago that goes into some of the hardware and costs. Whilst the costs can be negligible, it looks like a hella lot of fun!

[0] https://www.jeffgeerling.com/blog/2020/raspberry-pi-cluster-...

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#37

Post by kortex »

Using Ray distributed would be a better stress test. Computing primes this way probably isn't the best way to saturate cores. You are spending a lot of time doing python vm operations vs pure number crunching.

Using numeric arrays chunked into blocks of number ranges would be more efficient (and therefore "crunchier")

https://ray.io/

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#38

Post by zozbot234 »

rcxdude wrote: post #30
willis936 wrote: post #28

Earlier quoted context omitted.

That is not true. The energy efficiency will go down if you downclock because the static to dynamic power ratio will increase.

static to dynamic power ratio isn't efficiency though (and static power in modern desktop chips is tiny compared to the dynamic power). The dynamic power is not linearly related to processing speed (in fact it's much worse). If you downclock and undervolt a ryzen processor it will use much less power than the decrease in speed (e.g. from stock, if you drop performance by ~20% you might get a ~40% power decrease). Obv…

Static power ratio is increasing in modern processing nodes, to the point where a "rush to idle state" strategy starts to make sense because you can power down subsystems in idle states but you can't do that if you lower processing speed. The tradeoff would of course be different in a chip that was architecturally designed from the ground up for low-performance use, but that would be from things other than just a lower frequency for the same chip.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#39

Post by swiley »

smallpipe wrote: post #32

This is fun and all, but the benchmarks here aren't really what the author seems to think they are. This isn't "computationally expensive", the script is basically only control flow, where the CPU spend more time doing variable lookups than the actual computation. This means most of the pipeline width sits completely unused, whcih is a pretty large disservice to the M1 and the i5. There's also no control for the ther…

>no control for thermal throttling

there's no control because that's part of what he's measuring.

Re: Can My Water Cooled Raspberry Pi Cluster Beat My MacBook?

#40

Post by Quillbert182 »

thraway123412 wrote: post #23

2GB Pi is $55 on amazon. 4GB version is $62. That'd be $450+ for the eight pies. Ryzen 2700 launched at $300 (and tapered down to ~$200) and would pretty much run circles around such a Pi cluster. Just saying. These Pi clusters can be a cool and fun thing to build but if you're looking for compute power, you'd be better served by a mid-range desktop.

2GB pi starts at $35 at actual Raspberry Pi distributors, 4GB at $55, although there will probably be added shipping cost.
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