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Comparing the Chinese results with the American results, it seems that raising the wattage by a factor of 50 raises the thrust by a factor of 15000. That's somewhat hard to believe. On the other hand, the linked pdf from the Chinese team suggests that at just 3 times the wattage of the American group, they got 1500 times the thrust. I think there is some confusion somewhere.


Well, the natural world is full of non-linear and/or discontinuous responses, so it's not crazy if there's some sort of threshold at work.

But yeah, it's more likely there's some confusion in there.


It's an important question because the article claims "The applications for a device that functions as these appear to would basically replace every form of transportation and thrust invented by humans to date. Such a device would easily be used to make cars, planes, bikes, boats, etc., all more efficient, clean, and cheap." Given that the thrust required for a car would be something like 40,000N, unless the device scales far better than linearly, you'll need a 25GW power station in your car to even make it go.


NASA did acknowledge that at the power level the American team tested, thrust is generated in a more omnidirectional manner, which is focused into a directional jet as power levels are increased, so that might account for some of it.


It could be you aren't getting the full effect at the lower wattage?

What is the ratio of wattage to thrust, that's what I'd be curious about? And how efficient is it?

I guess change in kinetic energy can never be greater than energy inputted to the device, correct?


1 non linear

2 mianzi http://en.wikipedia.org/wiki/Face_(sociological_concept) & http://www.sciencedirect.com/science/article/pii/S0262407912...


It seems like an impossibly basic mistake, but confusing micro- and milli- newtons would make the math a lot more reasonable.


Not impossibly basic at all. Space missions have failed because of these kinds of basic math errors:



I almost want another failure so people will stop pulling this out as an all-purpose rhetorical showstopper.


Fly hearts are unrelated to mammal hearts. Flies belong to a completely different phylum. Pretty much everything about the organs of flies is different to humans. They don't have lungs, they don't have a brain, but a cerebral ganglion, they don't have a full stomach, but a stomodaeum, etc. More importantly, they don't have oxygen rich blood or red blood cells. I realise that flies are often used for genetic studies that have implications for humans, but I very much doubt this study says anything much about human heart health.


They are analogous, and an analogy is what we're after.


There are things we can do with flies that we simply cannot do with humans. Doing the research in flies is often a way for us to get an idea of how things may work in humans and others. Also, while we are physiologically different, we have quite a bit in common at the cellular level.


The trade-off of relevance to humans, and short generations (a day) seems to be best with fruit flies. I'm sure scientists have worked out what areas of research have worthwhile comparisons with mammals.


I would only use this if the first time I appeared on a website it asked me whether I wanted to add it to the list of sites I wanted to explicitly support.

That may seem intrusive, but otherwise this is going to (further) encourage content farms ripping off Wikipedia or just posting random material and optimising the hell out of its rankings (yes I know Google actively tries to stop this, but it just doesn't work well enough).

It's really important to distinguish money coming directly out of my pocket at someone else's whim, and advertising, where I need not purchase anything if I'm not interested.


Maybe not the first time (before you've seen any of the content), but generally, I like this idea.


The GMP (GNU Multi Precision library) guys found that the hand written assembly sequences (which were already 2-6x faster than that produced by a decent C compiler) could be sped up another factor of 2x by superoptimisation, at least of out-of-order CPUs.

Superoptimisation isn't only feasibly, it is actually quite practical. A factor of 2x across an already highly optimised library can cut your supercomputing budget in a grant by half. Whether you need 1 or 2 million CPU hours can make or break entire projects

These days, however, one can often do better with SIMD instructions. These often don't superoptimise well because the individual atomic operations they perform aren't able to be rearranged by the programmer. However, lots of existing supercomputers available for research still don't have chipset revisions with decent SIMD support.


The SIMD auto-vectorization is an off-shoot of this research.

But what excites me about super-optimization is to make functional optimization repeatable.

Let me give you an example of why I'd use it for more than HPC libs.

Assume you have a firewall system, which needs to determine whether a tuple of (srcip, dstip, dstport) is a safe one or not.

All 3 variables fit inside registers (assume xmm).

A rules engine as written traditionally would be a hashtable of some sort, always regenerated with a gperf hash (already we're in super-optimal territory partially).

But what if going to RAM is 300x more expensive than a SIMD sequence over 3 registers run a few hundred times?

Then writing a functional chunk of code which produces the same outputs for the same inputs, but without any storage system would be a killer feature.

That is sort of the problem where a super-optimizer can take a huge amount of data and turn it into bit-twiddling checks which find hidden invariants in each data-set.

Being able to take a bunch of rules which say subnet to subnet or port access patterns and compile it into a storage -less ACL mechanism (like bit 11 on port is 1, then DENY).

I'm almost certain these problems were solved in the past using a super-optimized FPGA as well (well, I would if I had the budget).

For me, being able to churn a dumb SWITCH loop through these systems is more interesting than chucking well written code into this.


I don't think this will be as successful as you might hope. Consider how many possible sets of rules there are. Call that n. The instruction sequence will need to encode log2 n bits of data, but you have no ability to tune the representation to say which inputs are likely.

Instructions aren't free, they still need to be loaded from RAM like data.


I wonder if it would be efficient to use part of those millions of CPU hours to optimize the programs themselves before running them?


You mean O(sqrt(n)), not quadratic. And given that the most obvious algorithm there is (check every possible divisor up to sqrt(n)) is O(sqrt(n)) arithmetic operations, I think it is fair to say this is not an important result.

I suppose it is a constant factor better than sqrt(n). But tricks along these lines go back to Gauss, at least.

Edit: ah I see, they claim O(n^2). Well I've never had an O(n^2) primality test before. I will put that in my kit of "do-not-ever-use-this" tools, just in case all my other ones break.


They even threw in a reference to a fields medallist on page 1 just to alert everyone that it was crankery.


Summary of paper:

All n = 0, 2, 4 mod 6 are divisible by 2. All n = 0, 3 mod 6 are divisible by 3.

Thus all primes are either 1 or 5 mod 6.

If n is composite and 1 mod 6, n = pq with p, q > 1 such that both p and q are both 1 or both 5 mod 6.

If n is composite and 5 mod 6, n = pq with p, q > 1 such that (wlog) p is 1 mod 6 and q is 5 mod 6.

What remains are the primes.

You have to look a little bit deeper than arithmetic modulo 6 if you want to say something interesting about the primes!


I'm very surprised by those figures.

Is that saying of 58 people studied, if 2 more people had stronger negative effects to placebo than Gluten then there'd be no discernible difference between placebo and Gluten?

How does that show a significant correlation?


I too thought gluten intolerance was all in people's minds, except for Celiac (which is a very serious affair indeed).

I had pretty bad intestinal problems for a couple of years. I had effectively ruled out gluten as a possible cause because in uni I had pizza boxes stacked to the roof.

Whilst reading a paper on a dietary study I remembered that croissants triggered severe intestinal issues for me. I began to wonder whether I had developed a sensitivity to gluten.

I cut gluten and my pretty bad intestinal issues ceased within days, with a total abatement after 2 weeks. That's been the case for 2 months now.

I also suffer from occasional (controlled) panic attacks. There has been at least a 50-75% reduction in those. (I was aware my panic attacks were exacerbated by the intestinal issues.)

Another interesting discovery in an article I read on HN is that metabolism is more affected by eating than light. So I tried not eating any calories after 10pm.

My normal waking hour is 11 am and has been for 15 years. By the first weekend after I started nil calories after 10 pm, I woke up at 7:30 am! (It's stablised to a more civilised hour now.)


I never had any gluten sensitivity issues until I was in my mid 20s. After a few years of really terrible symptoms a friend suggested I cut gluten out of my diet and my symptoms disappeared completely within two days.


In my case, I can't have had any severe gluten issues (at least not intestinal ones) until age 37.

Another really strange effect is that since stopping with gluten I have had very vivid childhood memories. I don't believe I had "brain fog", but something interesting happened.


Yea I had this experience as well. I also lost the ability to digest lactose, and got milk allergy/sensitivity(a little bit of both) issues as I got older.

I wonder if as we age, certain groups of people experience a failure of digestive enzymes across a variety of biological compounds.


Out of curiosity, was the intestinal issue the cause of some of the anxiety? Like you were afraid you'd poop your pants in public?


No, I don't believe it was a cause of anxiety. The bloating, excess (trapped) wind and associated discomfort caused very unpleasant sensations which triggered dizziness, panic, etc. If you've every been really constipated, you've had a similar sensation (but without the panic attack I imagine). In my case I had diarrhea though, not constipation.

Another odd one I discovered is jerky video playback (e.g. streaming on the web). That triggers a sense of unreality which can trigger an attack.


It's number 30 on the Tiobe list of programming language popularity. I'd hardly call that dead.



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