Recent submissions

Comment · 2 years ago
We (co-author here) are using EEVDF already since its in the latest mainline kernels. We havent noticed any major differences using the default settings, but plan to get around to tuning it later.
Comment · 4 years ago
I don't know what github is doing here, but I've seen this antipattern quite a few times in production at some big name companies...
Comment · 6 years ago
I am partial to the iPXE boot idea, you may find https://netboot.xyz useful.

As for how to prepare the images, you need a ramfs image with the root filesystem as a cpio file and a kernel as a vmlinuz file. You then serve these in a basic HTTP file server that your iPXE config points to.

Generating the vmlinuz file is pretty easy given a kernel. The cpio file is trickier. netboot.xyz recommends just grabbing a standard distribution. Otherwise this reduces to the problem of creating your own.

Comment · 10 years ago
"That allows a single bit to potentially hold two values at once, or for two bits to hold four values at once. Keep scaling those numbers, and you quickly end up with a device that can process data exponentially faster than today’s computers."

Yet another quote for the misrepresentation of science in articles.

Comment · 10 years ago
My question was about his claim in regards to the result in the paper. In practice, you are right but a consensus algorithm is still "partially correct" if it never decides on a value. It is only incorrect if different nodes decide on different values. For example, paxos does is not guaranteed to decide on a value. So timeouts are useful guessing tools, but I dont see how there is no consensus possible without them.
Comment · 10 years ago
You mean the OP's comment or mine? I agree with you if you mean the OP's comment. Though your quote refers to synchronized clocks. I dont think OP is referring to synchronized clocks, though your point that Lynch et al does not rely on timeouts is what Im getting at.
Comment · 10 years ago
"When used as a failure detector, timeouts are just a guess that something is wrong. (If they could, distributed algorithms would do without clocks entirely, but then consensus becomes impossible [10]."

Having just re-read Lynch's paper, can you explain what you mean here? I didn't see anything explicitly relying on time. It could be there is some implicit usage I didnt see. Additionally, the paper's impossibility result is about "perfectly correct consensus" which applies with and without clocks and then has a positive result for "partially correct consensus" (i.e. not deciding a value is a correct result). Im not sure which you mean when you say "consensus becomes impossible" as it is either already impossible (the perfectly correct protocol) with one faulty process or (to my understanding) not dependent on time (the partially correct protocol).

p.s. great article!

Comment · 10 years ago
Comment · 11 years ago
The article refers to 1180 MW of _power_. MW is joules/s and the unit of power is the watt (j/s). Your math talks about MegaWatt-Hours.

These are often confused in articles, do you happen to know if that was the case in this article? Did they mean 1180 MWH or 1180 MW as stated? Otherwise your yearly production calculation is very off. 1180 MW (j/s) would produce 10^7 MHW per hour.

Comment · 11 years ago
I figured performance came into it also. It would be nice to see some performance numbers though.
Comment · 11 years ago
Comment · 11 years ago
If a user realized that the "cost" of viewing the image was free, wouldn't the user disregard the cost on future instances of the experiment?

Did the experiment limit a user's participation to one time? Otherwise, the results might be skewed and the benefits exaggerated.

Comment · 11 years ago
Comment · 11 years ago
Ah, yep I see the race. Here is a fix: https://gist.github.com/sdab/d7ba036b2b7f4b5626cd

Thanks for the puzzle, its hard to find good concurrency problems.

Edit: Looked through your solution. You are right, we thought of similar things. I started out by wanting a multi condition variable, but didnt want to implement it :). I ended up getting something similar in a roundabout way.

Comment · 11 years ago
My c++ solution: https://gist.github.com/anonymous/7e6cc8f58e9cde1b6fda

I believe it follows all of the requirements. There is one glaring flaw which is that it uses a condition variable per 'wait_until_equal' call, though it uses only N mutexes. So this doesn't fall under the N^2 primitives (in the case of many waits), though its unclear to me if thats an official rule.

Im happy to listen to feedback or if someone sees an error.

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