Re: Mathematica and Lisp
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- Subject: [mg129721] Re: Mathematica and Lisp
- From: John Doty <noqsiaerospace at gmail.com>
- Date: Wed, 6 Feb 2013 21:29:44 -0500 (EST)
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On Wednesday, February 6, 2013 1:51:10 AM UTC-5, Richard Fateman wrote:
> On 2/3/2013 5:20 PM, John Doty wrote:
> You seem to think I haven't written Mathematica programs.
> Maybe looking at the appendix here would change your mind.
> Maybe not, though.
All this demonstrates is that you don't understand how to use Mathematica. =
All you know how to do is fight against it. You don't understand when to us=
e rules versus when to use the various algebraic tools. Your code is pointl=
ess: no trajectories calculated, no bridges designed, and it doesn't enable=
anything that Mathematica can't already do.
> > Considered as software failures, both of these occurred in application =
code and were not the result of programming language deficiencies.
> Was the code not written in a programming language?
> Even if it was written in assembler, that too is
> a programming language. I expect that the bug
> occurred because the programmer did not realize the
> semantics of the code.
In the Theravac case, the coders appeared not to understand the operation a=
nd hazards of the radiation therapy machinery very well. In Ariane case, I =
have heard that the coders concluded that overflow was impossible in the co=
ntext of Ariane IV, but that analysis was not redone for Ariane V when the =
software was reused. In any case, the fundamental failure in both cases was=
in systems engineering, not code. You shouldn't place much blame on the sp=
ark that sets you on fire when you walk around in clothes soaked with gasol=
> > Not all bugs are of equal importance. An error of 5.5E-79 in a Bessel f=
unction is very unlikely
> >to cause trouble in a practical application.
> One of the marvels of computing today is that it is possible to do so
> much in such a short time.
> One can execute billions of instructions a second. If only
> one in a million does the wrong thing, and is wrong only
> by a tiny percent, you can accumulate a whopping mistake
> in a second.
5.5E-79 is rather smaller than a tiny percent. The best physical measuremen=
ts are good to a few parts in 10^16. Assuming teraflop arithmetic, adding n=
umbers with errors of 5.5E-79, it'll take you about 4E45 times the age of t=
he universe to have errors add up to 1E-16.
> I've been using Mathematica to do practical work since version 1,
> > and I've never encountered a bug in its numerics.
> I guess it is my turn to wonder if YOU know much about Mathematica.
The difference is that I *use* it. You *fight* it.
> > Crazy results from numerical codes are a normal occurrence,
> > I don't find Mathematica to be unusually hazardous here.
> I guess I disagree on this point.
But you don't actually use numerical codes. You don't design bridges, compu=
te trajectories, or study turbulence. So your opinion is uninformed.
> >> This is pretty far afield from the original question which I
> >> think was somehow...s Mathematica somehow Lisp-like.... should I learn=
> > I'm unusual in that I write practical engineering code in Scheme (a Lis=
> > along with code for both science and engineering in Mathematica.
> I think that is unusual, but I count it as a good thing.
Well, I'm not so sure that using Scheme is so good: it means that few poten=
tial collaborators are willing to try to read my code. To the average engin=
eer or scientist, Lisp screams "forget your application and pay attention t=
o the cool computer science". Now, I actually know enough of that CS crap t=
hat I can see past it to reality, but most don't. I primarily use Scheme to=
access a collection of useful functions that are actually written in C, bu=
t have Scheme (Guile) interfaces. I think it would be much better if those =
interfaces were in a language friendlier to engineers, like Python. Scheme'=
s fine for me, with my eccentric background, but not for most others.
> Common Lisp (a Lisp dialect) is used in space computations --
> the Hubble telescope.
My old colleague Mark Johnston developed SPIKE for Hubble, but it has been =
and is used for other missions as well. I was involved in getting the ASCA =
and Chandra space observatories to adopt it for their operational planning.=
The last time I talked to Mark (a long time ago), he seemed rather unhappy=
with CL as an implementation language for a practical AI application. I do=
n't think he'd choose CL again if he had to rewrite SPIKE.
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