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Comment Re:At least they're not rolling their own. (Score 2) 138

You should not write a C++ interpreter. You especially shouldn't write an interpreter of a language that looks almost just like C++, but is different from it in unpredictable ways, some of which contribute to bad coding habits and/or make normal C++ more difficult to learn.

Strictly sequential files are a bad model for data if most of your time is spent constructing more-and-more elaborate subsets of that data. When we want to examine a subset, we practically have to make a complete copy of all the data falling into that subset. You want to make a small tweak to your selection? Make a new copy all over again.

Comment Re:At least they're not rolling their own. (Score 2) 138

Cycles are rarely the issue for us in HEP, and when they are, all we need is more nodes to split the problem into smaller pieces (wiki: embarassingly parallel problem). The actual computational needs are (typically) pretty small. The main bottleneck is usually data throughput. We discard enormous amounts of data (that may or may not be useful, depending on who you ask) simply because we can't store it anywhere close to as fast as we can make it (many orders of magnitude difference between the data production rate and the data storage rate). And then, when we're analyzing the data we've taken, our CPUs tend to sit idle while they wait on the disk to read another block of events, which then take a only a few cycles to add in to the necessary histograms. It only gets worse when the data is somewhere far away on the network. And it gets even worse when you want to select a subset of the data -- with our systems you have to make a full copy of the subset.

There are two big wins that modern big data has developed that we could benefit greatly from if the switchover costs weren't too high. The first is distributing data over many disks on many nodes and bringing the code to the data instead of bringing the data to the code. The more disks your data is on, the less you have to wait on seek times. The second is storing the data in a way that is not strictly sequential in a single set of files, so that if you want to look at a subset of the data, you can effectively do that without having to make a copy of that subset.

Comment Re: Proof is already from 1929 (Score 1) 158

You say to yourself something like:

Ok, here is some mathematical object called a state. What can I do with a state? Well, I can apply linear operators to a state. Given the properties of linear operators, there are some states that are unaffected (up to an overall scalar multiplication) by each operator. Call those "eigenstates". Call one of the operators the "position" operator. Find the eigenstates of the position operator. Now, I can compute, for any given state, how much overlap with each position eigenstate there is as a function of the corresponding eigenvalue. That overlap is a complex scalar function of position, which we can call a wave function, if we like.

It's actually much cleaner to start from this sort of abstraction and define the more concrete "wave function" from it than the other way around, partly because it allows you to more easily consider state spaces that, for example, don't have any operators with continuous eigenvalue spaces, like the spins of the ions in a ferromagnetic lattice, or the excitations of atoms/molecules in laser cavity.

Comment Re:Fixed the summary (Score 1) 158

Check chapter 9, (pages 237 and following), of the second edition of Principles of Quantum Mechanics by Ramamurti Shankar. Or, section 1.6 (page 18-20) and section 3.5 (page 110-118), of the second edition of Introduction to Quantum Mechanics by David J. Griffiths.

I'm sorry that I can't hyperlink to a physical book. But maybe you could go to your local public library and find a copy of one of them.

Comment Re:Fixed the summary (Score 2) 158

Correct fix: The uncertainty principle states that it is impossible for a particle to be in a state in which both the position and momentum (or any pair of observables represented by non-commuting operators) are exactly defined, or even well-defined beyond a certain limit determinable from the commutator of the pair of operators.

It has nothing to do with measurement, and everything to do with the mathematical existence of quantum states with certain properties. TFA is actually dealing with the observer effect, which does have to do with measurement, and which was Heisenberg's original intuitive idea.

Comment Re:Social Chaos (Score 1) 369

Better/more automation also means decreased costs for basic living necessities, which means that one will not need to work as much in order to feed oneself and one's family. It also means that welfare sufficient for necessities will be less expensive. It also means that those with high-paying jobs will have less expenses and a larger percentage of their income can be collected as taxes without seriously disturbing them, increasing the amount of tax revenue available for transfer payments.

One can imagine a future in which all necessities, entertainment, luxuries, etc., can be/are provided/created/transported via automated systems. There might not be any jobs, but there also might not be a need for any jobs.

Comment Re:Genius Idea (Score 1) 311

Back of the envelope calculation: [(10k miles per year) / (30 miles per gallon)] * (4 dollars per gallon) = 1.3k$ per year. Over ten years, 13k$. Tesla offers a pre-paid battery replacement (pay when you buy the car, get the new battery much later) for 12k$. So, if the battery lifetime is on the close order of ten years, then you're not far from the break-even point. If gas prices go up, or if you drive more, or if your gas mileage is worse, or if the battery replacement price comes down, then less than ten years will do.

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