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Comment: Re:This Is Slashdot's Forte (Score 1) 963

by Alef (#39871059) Attached to: Last Bastion For Climate Dissenters Crumbling

In other words, maybe We, the People have decided that we'd rather rise to the challenge of dealing with climate change as it happens than beggar ourselves in a futile and risible effort to preserve the planet in an eternal 1950s best-of-all-possible-worlds ideal state.

But those are not the alternatives. The 1950s world is long gone and lost already, and even if we stop emitting greenhouse gases right this instant the warming and its effects would continue to increase for some time. It is more like we are choosing between a pretty bad state and a (potentially) utterly fucked up state.

Comment: Re:007087 (Score 1) 510

by Alef (#39390851) Attached to: Van Rossum: Python Not Too Slow

I believe the local stack context in Lua is indexed. Because of lexical scoping, "local" variables don't necessarily reside on the stack, though -- they might be up-values captured by some function context which has subsequently escaped the stack frame where it was crated. I've never taken the time to learn exactly how they have solved that, but unless I'm grossly mistaken there are never any hash lookups for symbols that were declared local.

Global accesses always result in a hash lookup, however. I should mention "global" in this context may still be rather local, as you can replace the global environment (which is just a hash table) rather arbitrarily, for instance giving a set of functions their own shared global sandbox.

Nevertheless, I can't really see any reason why a language such as Python would fundamentally need to do hash table lookups for stack variables to keep its flexibility. It sounds more like bad language design. So I think my original point that dynamic languages can be fast still holds true (not that you were necessarily arguing against that).

Comment: Re:007087 (Score 1) 510

by Alef (#39390207) Attached to: Van Rossum: Python Not Too Slow

So that the compiler/JIT will only try extra-hard on the small section of code you really need to be fast.

That's how JIT compiling interpreters typically work. Most code is interpreted -- only functions that are executed often gets translated to machine code.

Some JIT compilers (called tracing compilers) take this a step further, and detect and translate hot code paths rather than functions. These paths can go across function calls, conditionals and loops, and as a result the most commonly executed code paths are essentially inlined as a machine code sequence. LuaJIT 2 is one example of a JIT compiler using this strategy. I believe Mozilla's TraceMonkey is another.

Comment: Re:007087 (Score 1) 510

by Alef (#39390057) Attached to: Van Rossum: Python Not Too Slow
I though we were discussing dynamic versus static languages, not interpreted versus native. I'm not going to deny that if you compare LuaJIT (dynamic language) to a state-of-the-art Java JIT interpreter (static language), Java wins. But not by any wide margin, especially if you consider that LuaJIT is developed by one guy (Mike Pall) more or less as a hobby project, whereas Java has received major corporate backing and development resources for more than a decade.

Comment: Re:007087 (Score 1) 510

by Alef (#39389969) Attached to: Van Rossum: Python Not Too Slow

Can a LUA object be treated like a hash table?

Yes, you certainly can. In fact, that is a very fundamental concept in Lua, around which the entire language is built. It goes even further than Python: there are no other data structures than (hash) tables in Lua, not even arrays or lists (unless you count string). Classes and objects are implemented using tables and are thus fully dynamic -- the core language actually has no concept of objects at all, but is flexible enough to allow the user to implement object orientation.

Comment: Re:007087 (Score 2) 510

by Alef (#39386677) Attached to: Van Rossum: Python Not Too Slow

The real reason why Python will still be slower than Java is because it's a much more dynamic language.

That's actually a rather bad excuse. Dynamic languages don't need to be that much slower. For instance, have a look at JavaScript V8 or LuaJIT 2 for some incredibly fast dynamic language implementations. If I recall correctly, last time I checked, LuaJIT was about a factor 3 behind optimized C code in the median case on the Computer Language Benchmarks Game (although it seems to be no longer included in that benchmark for some reason).

Comment: Re:120 gbps (Score 3, Informative) 199

by Alef (#38223958) Attached to: Inside the World's Largest LAN Party
Sweden isn't as small as you think. The average population density is around 20 persons per square kilometer, roughly the same as the US I believe. Sure, much of it is concentrated in southern parts, but people have had fiber to the home for close to a decade even in remote areas in the north, where the population density is one person per square kilometer.

Comment: Re:look at history (Score 1) 585

by Alef (#38166842) Attached to: New Batch of Leaked Climate Emails

Furthermore, it's a stretch to go from "we are causing earth to get warmer" to "we are fucking up the climate". Personally, I think there's a good argument to be made that warming is good and that we want more of it, despite some obvious short-term drawbacks.

Would you be willing to put money behind that claim and make a bet? I'd gladly hedge the risk.

Comment: Re:look at history (Score 1) 585

by Alef (#38159772) Attached to: New Batch of Leaked Climate Emails

Statistically significant with 95% confidence means that the probability that we would see data like those we have, in the case that there is no warming, is less than 5%. Now, if this level were 10%, we might say: Well, this data we are seeing could in fact just be a fluke -- we can't be sure. That's something entirely different from saying that data indicates there is no warming.

If you want to claim that there has been no significant warming, you would have to compute the probability that we would see similar data in the event that there is warming going on. This probability will likely be nowhere near as low as 5% or even 10%.

The end result is that while the data doesn't indicate there is warming with statistical significance (only almost), nor does it indicate that the temperature has remained flat, with any statistical significance. That is, the data for this particular period tells us nothing with certainty -- we simply have too little of it. But if anything, the data that we do have support the global warming hypothesis more than it supports the random variation hypothesis.

Trying to use this as an argument, not only against global warming, but against any precautions that even consider global warming a possibility, is frankly idiotic, especially considering all the other data that we have.

Comment: Re:look at history (Score 1) 585

by Alef (#38152800) Attached to: New Batch of Leaked Climate Emails

You're not listening to what I'm saying. "Not statistically significant" only means "data does not prove it beyond 95% certainty". So if the data are sufficient to be 94% sure there has been warming, we still do not call it "statistically significant". It does absolutely not mean that the data indicates there has been no warming. Quite the contrary, it does, just not to the degree that we by convention call "certainty".

Also, it is hard to be 95% certain of any climate hypothesis if the time span is to short, because any trend will be overshadowed by local noise.

But for all intents and purposes, it makes no difference whatsoever whether we are 95%, 90% or 80% sure that we are fucking up the climate. The odds suck, regardless.

Comment: Re:look at history (Score 1) 585

by Alef (#38150826) Attached to: New Batch of Leaked Climate Emails

Either you don't understand basic statistics, or you're just trolling. Regardless of which, what the first link you provided is saying is essentially something like this: "Because the time span from 1995 to 2009 is such a short period to measure climate over (which by definition is the average over a long period of time), we can only be 90% or so certain that long-term average temperature has continued to increase during that period.". How you can get that to a confirmation of no global warming is beyond me.

Relevant quote from the BBC interview:

B - Do you agree that from 1995 to the present there has been no statistically-significant global warming

Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods.

Comment: Re:The saddest thing is that there are not two sid (Score 3, Insightful) 585

by Alef (#38142292) Attached to: New Batch of Leaked Climate Emails

Probably. But I'm honestly growing a bit ambivalent as to how one should approach people about climate change. Normally, I would say civil discussion is the most effective way to reach someone, but considering the seriousness of the matter, when nothing happens at some point you ought to start getting angry.

If somebody were pouring gasoline onto my house, and were about to set fire to it while insisting that I have nothing to worry about because surely nothing is going to happen, I wouldn't be very civil with them. We more or less have the same situation right now, only at a much slower pace.

By refusing to accept facts and take responsibility for the situation we have created, millions will be forced from their homes around the world, people will die from starvation and floods, species will become extinct, etc. etc.. How can we in good conscience stand by and be civil about it as others spread lies and misinformation for their own personal gain?

Comment: Re:Is this technically feasible? (Score 1) 356

by Alef (#38119490) Attached to: Pakistan Bans 1600 Words and Phrases For Texting

That's 16kB/s. Let's say each word take 1000 cycles to test for, which should be on the high side since it assumes you can't use, say, a trie to take advantage of common word roots, or use pattern matching accelerators (which are quite common in this space [google.com]). 16kB/s * 1000 * 1600 = 25.6Gcyc/sec.

I'd say being on the high side there is a bit of an understatement. Using a trie, as you suggest, you'd probably be able to check a typical word against the entire dictionary less than 100 cycles, so your estimate is probably overshooting by four or five orders of magnitude.

Odets, where is thy sting? -- George S. Kaufman

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