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Comment: Re:Phones yeah (Score 1) 227

by Mr Z (#46691899) Attached to: Nanodot-Based Smartphone Battery Recharges In 30 Seconds

Yes, imagine a world where the laws of thermodynamics don't apply.

The peak theoretical efficiency of an internal combustion engine is bounded by the efficiency of an equivalent ideal Carnot cycle, which if I remember my ME301 Thermo class, is a bit below 40%. Wikipedia backs me up on this, quoting a limit of 37% for a steel engine block. That jibes with what I remember learning in Thermo.

To get 80% efficiency out of gasoline would require a different method of releasing its energy than an internal combustion engine.

Comment: Re:Voltage != Power (Score 2) 208

by Mr Z (#46646435) Attached to: USB Reversable Cable Images Emerge

You are correct. I got my wires crossed. I actually have a 7805 replacement here in my "lab" that is an actual switching regulator. And for some reason I had mentally bucketed it with LDOs, which as you noted, are just low-dropout varieties of linear regulators. And yes, switching regulators like these are a little pricier, although I believe with the RECOM R-78xx series you're just paying for the convenience of swapping out a 7805 space heater without touching the rest of your circuit. :-P

Comment: Re:Lemme posit this... (Score 1) 100

by Mr Z (#46541059) Attached to: College Grads Create Fake Tesla Commercial That Elon Musk Loves

Because, when it comes to car commercials, ad agencies are bound by so many rules and regulations regarding depictions of reckless driving and such things that it becomes almost impossible tp create a cool car commercial without running the risk of going to court over it (both the ad agency AND car manufacturer).

And yet, this commercial had zero driving at all!

Comment: Re:Welcome to Lamport's Bakery! (Score 1) 40

by Mr Z (#46531603) Attached to: Turing Award Goes To Distributed Computing Wrangler Leslie Lamport

Ok, the statement I made in my third sentence above is imprecise to the point of being inaccurate. The exact property, as described by Wikipedia:

The original proof shows that for overlapping reads and writes to the same storage cell only the write must be correct. The read operation can return an arbitrary number. Therefore this algorithm can be used to implement mutual exclusion on memory that lacks synchronisation primitives

So the part about not needing "properly arbitrated memory access" is mostly true—a read that collides with a write to the same location can return garbage. Writes still must update memory properly, and presumably must be sequentially consistent.

Comment: Welcome to Lamport's Bakery! (Score 1) 40

by Mr Z (#46531583) Attached to: Turing Award Goes To Distributed Computing Wrangler Leslie Lamport

My first encounter with Leslie's work was Lamport's Bakery. It's a serialization primitive with some surprising properties. For example, it doesn't require properly arbitrated access to memory as the initial value read from memory on entrance to the "bakery" actually doesn't matter!

Dr. Lamport was actually kind enough to reply to an email of mine regarding said primitive. I was optimizing a version of it for a multiprocessor device we were making where I work, and I had come upon what I thought was a clever optimization. (I actually vectorized a portion of the algorithm by way of the "unroll and jam" transformation, so I could test the state of multiple processors in parallel, rather than in serial order as described in the algorithm.) He actually took the time to respond to my email, and was quite gracious. His reply:

In the Bakery Algorithm, process i must wait until a certain condition holds for each other process. The order in which it checks for the different other processes does not matter. So, the algorithm can be parallelized in the manner you suggest.

The only time I was more thrilled on a topic like this was when Dr. Knuth replied to mail I sent him regarding a particular algorithm in Volume 4 of TAOCP. I actually received a hand written reply. Well, he hand wrote notes on a printed copy of the email I had sent to his TAOCP feedback address. Dr. Knuth also encourages me to let all my friends know how much I like TAOCP. So, consider yourself informed: I think Knuth's The Art of Computer Programming series is worth its weight in gold, and if you consider yourself a computer scientist or computer engineer, you should consider getting yourself a copy, and investing the time to at least skim it. (Let's face it, to truly understand everything in there would require as much time as Don put into writing it.)

Comment: Re:Quick change needed [Re:Stop] (Score 1) 349

by Mr Z (#46470497) Attached to: Crowdsourcing Confirms: Websites Inaccessible on Comcast

I just checked it now on my end and it seems to be fine. Maybe it was just a transient failure?

$ host eztv.it
eztv.it has address 162.159.244.249
eztv.it has address 162.159.243.249
eztv.it has IPv6 address 2400:cb00:2048:1::a29f:f3f9
eztv.it has IPv6 address 2400:cb00:2048:1::a29f:f4f9
eztv.it mail is handled by 10 ezmail.es.
$ grep nameserver /etc/resolv.conf
nameserver 8.8.4.4
nameserver 8.8.8.8

Comment: Re:I've experienced it (Score 1) 352

by Mr Z (#46415707) Attached to: Vast Surveillance Network Powered By Repo Men

I wonder if that was what was up with a truck I saw a few months back, with a huge ol' camera on the side. It was just a boring black pickup truck, and just one camera on the driver's side.

I've seen the Google Car, and it was much smaller, painted rather obviously, and had cameras facing multiple directions.

The superior man understands what is right; the inferior man understands what will sell. -- Confucius

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