91–100 of 125 posts
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Worse, heat dissipation is a major constraint for spacecraft and satellites because you can only radiate heat away as infrared photons.
Amazing considering how much heat travels from Sun (and punches through atmosphere) to Earth surface. Didn’t realize there was that much of an insulation property.
It's very interesting how abtracted away HPC sometimes looks from hardware. The books seem to revolve a lot around SPMD programming, algo & DS, task parallelism, synchronization etc, but very little about computer architecture details like supercomputer memory subsystems, high-bandwidth interconnects like CXL, GPU architecture and so on. Are the abstractions and tooling already good enough that you don't need to worr…
I wrote scientific simulation software in academia for a few years. None of us writing the software had any formal software engineering training above what we’d pieced together ourselves from statistics courses. We wrote our simulations to run independently on many nodes and aggregated the results at the end, no use of any HPC features other than “run these 100 scripts on a node each please, thank you slurm”. That ap…
I've seen similar things at the intersection of bioinformatics and genomics. Computers are getting bigger but the genomes aren't, and tasks that require distributed computing are getting rare.
I would have thought, that after some 30 years of high performance distributed computing, the requirements were well known and at least the protocol for command and data exchange could be fixed. Apparently not so.
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> Liquid cooling is serialized in a node. Two sockets? I've seen tests done on heavy PC loops (ie multi-GPU) both high-flow and low-flow, as well as on car engines, in different coolant flow configurations. The results from all of those are that the water doesn't rise meaningfully in temperature between components. Unless I did my back-of-the-napkin math wrong, this seems reasonable. If you have a single 10mm ID pipe…
In our system every node gets inlet water at the same temperature via parallel piping, but when it’s in node, it goes through processors first, then RAM, then PCIe and disks. Delta T between two sockets is 5 degrees C, and the delta T between input and output is around 15-18 C depending on load.
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> we attempted to install a medium size HPC cluster in a well-known commerical Datacenter and network provider. The commercial of the DS almost fall from his chair when we announced the power requirements. Heh. We tried it too. They didn’t believe that a single node used their entire rack’s budget at first.
Sounds fascinating. Can you give any more details? What kind of nodes are they and how they differ from "traditional" DC hardware, say from Supermicro?
[1]https://www.supermicro.com/en/products/system/gpu/5u/sys-521...
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Worse, heat dissipation is a major constraint for spacecraft and satellites because you can only radiate heat away as infrared photons.
Doesn’t have to be infrared but yeah, space isn’t “cold” so much as it’s an insulator.
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C++ programmer and educator here. This (volume 3) is well organized good beginner level teaching material. You probably know most of it already. I was looking for range-based for loop, std::array and std::span and happy to see that they are all there. Because this book relates to HPC, I'd add a few things: Return Value Optimization, move semantics, and in the recursive function section a note about Tail Call Optimiza…
That's great - thank-you. Assuming I work through this quickly, what resources would you recommend as a follow-on?
- Modern object initialization using {} and ().
- std::string_view
- std::map
- std::stack
- Emplace addition of objects to containers like vector and map.
- Smart pointers (std::unique_ptr, std::shared_ptr and their ilk).
- Ranges library.
- Concurrency support library (std::async, std::future, std::thread, locks and the whole deal).
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It always made me wonder why liquid cooling wasn't more of a thing for datacenters. Water has a massive amount of thermal capacity and can quickly and in bulk be cooled to optimal temperatures. You'd probably still need fans and AC to dissipate heat of non-liquid cooled parts, but for the big energy items like CPUs and GPUs/compute engines, you could ship out huge amounts of heat fairly quickly and directly. I guess…
Because it’s complex. Even more complex than “engineered” air. You need two circuits, and a CDU between them. Coolants needs maintaining. You add antifreeze, biocides, etc. Air is brute force. It cools everything it touches. Liquid cooling is serialized in a node. Two sockets? Second will be hotter. HBA not making good contact? It’ll overheat. You add extensive leak detection subsystems, the amount of coolant moving…
I guess it could be bad past some %, but there's a probably a point where it's worth it.
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Doesn’t have to be infrared but yeah, space isn’t “cold” so much as it’s an insulator.
at ~2 kelvin I'd have thought you can radiate away a truckload of heat surely
But not convect. Hence why it’s much, much harder than removing heat on Earth.
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at ~2 kelvin I'd have thought you can radiate away a truckload of heat surely
You can radiate easily. But not convect. Hence why it’s much, much harder than removing heat on Earth.