Sorry about "square" I meant a cube. In any case, it's should be obvious from the context that it should be a cube.
I gave an example of how one can perform back of the envelope calculations, without a calculator, to estimate the level of effort required. It illustrates a principle.
Originally Posted by
uszkanni
This post is a bit muddled...
Kinda "mixing your metaphors" here; 20km above the earth but each cell being 1/7th mile (area, I presume, hence square miles).
Yes a bit muddled. I should not have posted it from my phone. A proper keyboard would have been better.
Your presumption is totally off the mark. You did not have to presume anything to talk about area. I had already made the mistake of calling it a quare. I would have commended you had you presumption had led you to talk about volume.
I used mile to make my point about size of the cell, because most people here understand miles better.
This comment reminds me of your last comment here about "an ad hominem attack".
Originally Posted by
uszkanni
That notwithstanding, the math doesn't work. The earth's radius is about 6380 km (on average), add 20 and we get around 6400. The surface area of such a sphere is about 514,718,540km. Divide by a trillion (1,000,000,000,000) and you get a cell that's around .0005 km in area. That's a cell about .0002 square miles, which is a whole lot less than 1/7th of a mile.
Math does work. Once you get out of the mindset that what's stated is wrong, apparently misled by my use of "square" in stead of cube.
Both uses, one metre cube/square and one square/cubic metre are acceptable but mean different things. So 1/7th mile cube as well as 1/7th mile are absolutely correct.
Originally Posted by
uszkanni
It's been a very long time since I last worked on GCMs
It's astounding that someone who worked with GCMS would not consider the possibility that I might have mean cube.
Originally Posted by
uszkanni
but, in those days, the typical lat/lon resolution was around 2.5/2.75 degrees (or some such), which meant that each atmospheric level had about 90x72 cells.
I
And how accurate was it? At what level did you work? I mean what level of detail were you seeking? I have not made, and I am not making any definitive statement about what cell size is adequate.
Originally Posted by
uszkanni
I think that nasa/noaa/ncar are looking at GCMs with grid resolutions of around 3-5km (but I've been away from that field for many, many years, so don't hold me to those numbers) which means that each level would contain about 20-50 million cells, nowhere near a trillion.
I did not make any claim about being a GCM expert, just gave an example of how anyone, can do some simple calculations to estimate level of effort. If you worked with GCMS, which I have not, but know from simple commonsense, that those calculations are reiterative. I did not even give any details about what kind of calculation is done for each cell? I used one arithmetic operations per element, which A GCM person would know is ridiculously low, show that we are already to a very very large number of operations.
Originally Posted by
uszkanni
And why 20km? The difference in surface areas of a sphere 6380 vs 6400km is less than 1%.
Again, I have not presented a GCM model. It's a simple illustration of estimating computational effort. A simple division of a portion of the atmosphere into cubic cells does not make a GCM. Any GCM expert would no that. I think you started with the assumption that my GCM model, which it is not, is wrong.
Originally Posted by
uszkanni
What makes you think NSA is bothering with 128 bit encryption?
If I knew what NSA was using, I would not be posting it here.
Originally Posted by
uszkanni
Ask instead, for example, how much computing power you need to monitor a whole lot (ie, a nation's worth) of phone conversations (especially cell and sat) and apply word spotting software to pull out "interesting" conversations in real-time. If you think this isn't happening then I would suggest you go back and review the now public disclosures of Bush's (Bush the Lesser, not Bush the Elder) warrant-less wiretaps.
I dodn't know, but I don;t think monitoring conversations, is a computing intensive operation, and computing power alone would not do it. Quality of sensors and their locations is just as important.
Originally Posted by
uszkanni
This comes off sounding a bit snide, like an ad hominem attack.
I disagree. The statement cited no reasons. It was a belief.
You took my off the cough remarks designed to show how one can estimate requirements for a computational efforts as an instruction on GSM models and an explanation of NSA functions.. I picked two simple examples. I am not a GCM expert, nor do I work for CIA/NSA etc. Are you? If I were, I would not be posting here.
Here is how I did a cell calculations. Again. DON"T challenge my assumptions because they are not directives for a GCM model.
I assumed, that most of the mass of the atmosphere is within the 20 Km layer above the surface of the earth. Hence only that layer interacts with the sun and the universe. I calculated voume of that layer, which is a spherical shell of thickness 20Km. I Chose an arbitrary number of cells, a million/billion/trillion to estimate the size of each cell. All other details were ignored as they are not necessary for my point.
For NSA, I picked a simple task that most people can identify with. Breaking a code, with brute force, trying every possible combination.
Research in a field always requires a lot more effort and expense, than running field applications based on that research.
If you were slighted by my comment that NSA probably does not have the most powerful computers, I apologize. Rest assured that I don't value a person by the size of tools they have. Nor would my opinion deprive NSA of asking for more powerful computers. It was an opinion.