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R.M
4:04 AM
@Verde sure
 
too late
it was my "pattern name asymmetry" q
 
R.M
oh, good I was late then... I got 8 up votes instead :D
 
:D
 
5:09 AM
New WRI advertisments
 
5:29 AM
@Guillochon You may want to look At my answer here: stackoverflow.com/a/8363520/615464
 
 
12 hours later…
5:06 PM
@belisarius, wow, that was sudden, you were Verde a minute ago right?
Still @Verde in here
 
@Rojo Yep, slow cache. Surely it is the CDS
@Rojo The FE has a faulty event queue manager. So sometimes the event "Locator drag started" fails to propagate in a slow machine, and the initial action of Dynamic[] is never executed. Damn bugs
 
That sucks
 
@Rojo Have you seen my poison diffusion experiment above?
 
No
 
the apple
 
5:15 PM
Hahah
I was testing SystemModeler the other day and found a bug that was quite basic
 
It's almost beta, I guess
@Rojo How are the links among subsystems modeled? Do you have to specify them all, or is there some "intelligence" behind the scenes?
 
R.M
@belisarius they should've gone with a toast
 
@R.M Who? sir Isaac and Stephen?
 
@R.M I wonder how long you'd have to run rule 30 to create a universe in which Stephen Wolfram's face appeared on a piece of toast?
 
R.M
@belisarius no no... I was referring to what Oleksandr said
@OleksandrR. I'm sure SW has rigged it so that the right seed will lead to it in 42 steps
 
5:30 PM
@R.M Sorry, your link points to the apple image
@OleksandrR. Do you read Spanish?
 
R.M
@belisarius Yes, I was linking to that, but I was referencing the idea that Oleksandr mentioned... In other words, he understood what I meant
 
@belisarius no, afraid not.
 
R.M
Sorry, I'm trying hard to reach your 1% :)
 
@R.M I suppose because of the principle of computational equivalence we'll just have to run the experiment to find out!
 
5:33 PM
@OleksandrR. A pity ... there is a nice song about that. All things start to transform in the same character, street names, companies, car models, etc etc ...
@R.M I know a guy who has an American flag somewhere
no miracle at all
@R.M Don't engage in trying to upset me. I am too lazy to fight
 
It doesn't look very well toasted. That's all part of the miracle, I suppose.
 
R.M
we just need that on a toast now
Huh... looks like several others had the same idea:
 
Haha, that is brilliant.
 
R.M
@belisarius The Mary there referred to Paul's mother
 
5:46 PM
@R.M You are a nihilist
Now come and tell me that "Lucy in the Sky ..." is dedicated to an astronomer
 
R.M
haha, no. but it really was dedicated to his mother
 
@R.M yeah yeah :)
 
R.M
That's what should be on my toast
or with my toast
 
are you eating THAT?
 
R.M
Although, I'd prefer rum/whiskey/beer over that
 
5:50 PM
and a few jalapeños
 
R.M
Make it habaneros
 
R.M
Are they hot?
 
@R.M Not VERY hot, but enough to enhance your thirst
like a jalapeño more or less, but tastier
 
R.M
Nice. I have a little pepper garden with about 5-6 different varieties... I don't have jalapeños anymore, but been thinking of growing it again next season
They weren't as hot as they should've been
but hot or not, they taste good when pickled
 
6:03 PM
@R.M To enhance the the capsicum content, try to keep the soil as dry as the plant can afford.
 
A friend of mine is growing these. Unfortunately I can't do so because I don't have a greenhouse, but he offered to give me some of the fruits... looking forward to trying those!
 
R.M
@belisarius Yeah, that works. In this case I think it was more due to cross-pollination with a very mild/sweet variety nearby
 
@R.M yep. that happens. You can pollinate manually, but that is a lot of work
 
R.M
hehe, yeah.. it indeed is. There's good bee activity and wind here, so I wonder if I'll be able to affect the pollination in any specific way...
 
@belisarius didn't know that! so, i've definitely been overwatering my jalepenos and poblanos
 
R.M
6:16 PM
@EliLansey usually when people see dark (sometimes soft) spots on their pepper fruits, they think it's drying because of lack of water and then over compensate. Actually, the opposite is true
 
@R.M very interesting. good to know.
problem is, our vegy patch is small
 
@EliLansey As far as my experiments went, the poorer and less watered the soil, the hottest the chilis
 
and overcrowded mostly with tomatoes, peppers and beans are hiding in the shadows
@belisarius ok, i'll try that next year
 
R.M
@EliLansey To be a little more specific, it's due to erratic watering. So they think they're underwatering and then overwater all at once, and forget about it the next few days... rinse and repeat
 
6:21 PM
@R.M ok! it's always easy to be irresponsible ;-)
 
R.M
@EliLansey It's amazing, but you can never really keep a regular watering schedule if you're doing it by hand (unless if you're a retired old man who has nothing else to do)
 
@R.M i have my garden on a watering timer
something like this
 
R.M
That's good! For nearly a year, I put aside installing piping and drip systems and watered with a hose every few days... inevitably, your estimate of "how much" wavers and you get busy occasionally, etc...
I thought they were doing fine, but I realized how under watered (and erratically watered) they were when I finally got around to doing all the work and installing it. In the 2 months since I installed it, the plants have been flowering copiously, looking lush and greener than ever and grown more than in the whole year prior to that!
Anyway, I better get back to writing this darned paper. ugh.
 
R.M
7:16 PM
@belisarius You still around?
ok, never mind... fixed it
 
7:51 PM
@R.M I am now
 
8:50 PM
A gardening chat!
 
9:17 PM
Are there any tricks to make FullSimplify faster? Or an alternative to it? It goes horribly slow if I include any assumptions...
 
R.M
9:40 PM
@Guillochon depends... do you know of any tricks that would be helpful for your problem (i.e., analytical insight)?
Also see this:
19
A: What is the difference between a few simplification techniques?

R.MThe primary difference between Refine and the two *Simplify functions is that Refine only evaluates the expression according to the assumptions given. It might so happen to be the simplest form when evaluated, but it does not check to see if it is indeed the simplest possible form. You should use...

You could try playing around with TimeConstrained and TransformationFunctions, etc... not promising anything, but good to consider them.
 
I can send you the snippet of code, it's not terribly complicated actually
 
R.M
if it's not big, you can post it here... again, no guarantees :)
 
well, maybe you can identify some strategy i could use to simplify it
the first few fullsimplify calls do okay, but as the expression gets more complicated Mathematica just hangs and hangs
 
R.M
Do you know what the answer should look like or are you just hoping that it'll be something "cute"?
 
I know the answer is going to be a bit messy
 
R.M
9:48 PM
It does look pretty messy...
 
But I'm trying to get it into a functional form that's as simple as possible
For use in a compiled language
 
R.M
Haskell?
 
Fortran :-)
Ideally, I would want a simplification procedure that would minimize the number of floating point operations...
but that's probably pretty hard to do
 
R.M
Yeah, probably. There's no easy way to do that, I'm afraid
but although the final expression looks a bit messy, it's not all that terrible.. there's a fair bit of repeating terms and if you pull all of those out, it'll probably be a simple expression
 
yeah
actually, maybe there's a way to have mathematica identify repeated functional expressions?
and then replace them?
 
R.M
9:52 PM
for instance, several Sin[ArcSin[aspin]/3] and Sin[1/3 (2 π + ArcSin[aspin]/3)] peppered around
@Guillochon whatever you do, don't use pattern matching!
 
It seems to me that what one could do is count all sub-expressions
And then you replace the one with the most matches
and you repeat that process unless there are no repeated sub-expressions
@R.M It's a good thing I barely know how to use pattern matching... :-)
 
R.M
Well, you might be able to get away with most, but the chances for messing up/errors/inflexibility are high
See this question for instance...
So yeah, you could try it (it might work), but it is barely a sheet of paper's worth if you write it out, so I would recommend that :)
Good ol' pen and paper can still be useful :)
 
Yeah, I know...but I make mistakes!
Actually, it would be desirable to have this because I need to take an integral of that resulting expression
...although it's very likely to not be integrable
 
R.M
haha, I'm certain. I've seen mathematica choke with just one or two inverse trig functions, so... :)
(assuming you want Integrate and not NIntegrate)
anyway, gotta go now. Bye
 
Thanks for your help
 
R.M
10:03 PM
"help"... I didn't really do anything :)
 
Well, you convinced me to not try much harder... :)
 
10:19 PM
Hey everyone, would any of you care to check the result of Integrate[Cos[a] Exp[I k Cos[a - b]], {a, 0, 2 Pi}]? Mathematica gives 2 I Pi BesselJ[1, k] but I think it's missing a factor of Cos[b] and I want to make sure I'm not crazy.
 
@R.M how can one do anything without using pattern matching in a term-rewriting langage?
@Guillochon use Experimental`OptimizeExpression
@DavidZaslavsky I concur. Comparison with the numerical integral confirms it.
 
@OleksandrR. thanks!
 
@OleksandrR. Hmmm, how am I supposed to interpret the output of this?
 
@Guillochon well, it factors out the common subexpressions for you. The result is still a bit messy, but the number of operations is reduced.
 
R.M
10:43 PM
@OleksandrR. well, yes, but that wasn't the point really, since I followed it with an example. I meant that structural manipulations shouldn't be used for mathematical manipulations
 
@OleksandrR. Hmm, I didn't get that at all, I got things like Compile`$13
 
@Guillochon I manually cleaned it up a little.
I had changed all of your FullSimplify to Simplify (FullSimplify takes too long), then Experimental`OptimizeExpression[%, "OptimizationSymbol" -> var, "OptimizationLevel" -> 2]
 
R.M
@OleksandrR. what does "OptimizationLevel" do?
 
@R.M same as it does for Compile.
Oh yeah, that's undocumented...
It's basically an "aggressiveness" option--how dedicated will it be in factoring out all the common subexpressions? Possible settings are 0, 1, or 2. (But not All, unlike for Compile.)
After common subexpression elimination is done to this extent, any Fortran compiler worth its salt ought to be able to produce reasonably decent code.
 
R.M
11:03 PM
Thanks, didn't know about that!
 
BTW, setting "OptimizationLevel" -> 2 for Compile on normal procedural code seems to be dangerous as it can drastically re-order operations. But for pure mathematical expressions like this I think it is safe.
 
R.M
11:15 PM
Nice, this will certainly come in handy. I do remember seeing Experimental`OptimizeExpression before though... probably mentioned by you here. Is there a question on the site?
 
11:27 PM
@belisarius Makes sense; if the plant senses that the conditions are harsh, it would try to produce more of the chemicals that are supposed to prevent other living things from eating it... ;)
 
@J.M. That's from a darwinian POV. Intelligent design would argue that the plant, knowing its fellows are dying, commits itself to saving Tabasco's business.
 
That is, if it has cognizance that there are living things that are actually interested in its noxious products... :)
@belisarius BTW... it's not easy being green?
 
11:45 PM
@J.M. My Third personality got depressed and intended to split out. We hold a Swiss kind of government conclave and decided to send Verde to Afghanistan in order to reestablish our unity. He is now working as a drone stewardess.
 

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