28 Nov 19:02 2015

### Carminati-McLenaghan invariants with ctensor

Viktor Toth wrote:
> The most important suggestion that you saw I think is that loading the
> package should not result in any significant computation. But that could be
> easily taken care of by following the logic in ctensor itself, namely that
> prerequisites (e.g., the metric, the Ricci tensor) are computed only when
> needed, not at package load time. I would consider this a given if I were to
> incorporate your code into ctensor. Which I am very inclined to do, since it
> seems eminently useful; right now I am tied down with other work and I don't
> want to distract myself (Maxima is so much fun!), but I may get to it in a
> couple of weeks' time.

OK, I've made the following changes:
- No computation is done when the package is loaded.
- There is some basic documentation in the README file.
- The documentation explains how to start over with a new metric within the same program.
- Simplifications are turned on by default, but there is a provision for turning them off.

I think this takes care of all the issues pointed out by Daniel Volinski, except possibly an issue with the
Kerr-Newman spacetime. Daniel, if you're unable to make that work, could you post the complete code of

There are some notes in the README about some things that I would still like to do at some point but cannot
presently do or consider to be a lower priority.

-Ben Crowell

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27 Nov 22:56 2015

Hello all and happy Thanksgiving to those that recently celebrated it,

I only recently heard of p-adic numbers. I was introduced to them through this video: https://www.khanacademy.org/math/recreational-math/3blue1brown/inventing-math/v/what-does-it-feel-like-to-invent-math

Basically, the video explores how sum(p^k, k, 0, inf) = 1/(1-p), when 0<p<1, but what does it mean when p is outside of that range? It attempts to make sense of p=2. The video does this by redefining distance (using a p-adic metric). Using a p-adic metric, the sum converges to the value specified by the equation, namely -1.

I remember asking a while back about the statement 1+2+3+4+...=-1/12 (the normalized/regularized value). This value also agrees with the Zeta function. I mostly understand how to get -1/12 using analytic continuation. I've also seen a "proof" that just shuffled and partitioned infinite sums to arrive at the same answer as well. Now I have heard about p-adic norms, I wonder if they can be used with the Zeta function. If so, which p would we need?

Anyways, I have real no use for them, but still wanted to explore them a bit more. Has anyone on here used p-adic numbers? What are some good references? Does Maxima support p-adic numbers?

Thanks in advance for any information you provide.

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27 Nov 14:56 2015

### Maxima for $5 Raspberry Pi FYI -- Everyone on Earth can now afford to run Maxima on this$5 computer.

Has anyone checked what the current version of Maxima running on the Raspbian version of Linux is?

https://www.raspberrypi.org/blog/raspberry-pi-zero/

Raspberry Pi Zero: the $5 computer Of all the things we do at Raspberry Pi, driving down the cost of computer hardware remains one of the most important. Even in the developed world, a programmable computer is a luxury item for a lot of people, and every extra dollar that we ask someone to spend decreases the chance that they'll choose to get involved. Private Video on Vimeo https://vimeo.com/146893658 The original Raspberry Pi Model B and its successors put a programmable computer within reach of anyone with$20-35 to spend.  Since 2012, millions of people have used a Raspberry Pi to get their first experience
of programming, but we still meet people for whom cost remains a barrier to entry.  At the start of this year,
we began work on an even cheaper Raspberry Pi to help these people take the plunge.

Today, I'm pleased to be able to announce the immediate availability of Raspberry Pi Zero, made in Wales and
priced at just $5. Zero is a full-fledged member of the Raspberry Pi family, featuring: A Broadcom BCM2835 application processor 1GHz ARM11 core (40% faster than Raspberry Pi 1) 512MB of LPDDR2 SDRAM **** More than enough for Tor **** A micro-SD card slot A mini-HDMI socket for 1080p60 video output Micro-USB sockets for data and power An unpopulated 40-pin GPIO header Identical pinout to Model A+/B+/2B An unpopulated composite video header Our smallest ever form factor, at 65mm x 30mm x 5mm Raspberry Pi Zero runs Raspbian and all your favourite applications, including Scratch, Minecraft and Sonic Pi. It is available today in the UK from our friends at element14, The Pi Hut and Pimoroni, and in the US from Adafruit and in-store at your local branch of Micro Center. We've built several tens of thousands of units so far, and are building more, but we expect demand to outstrip supply for the next little while. One more thing: because the only thing better than a$5 computer is a free computer, we are giving away a free
Raspberry Pi Zero on the front of each copy of the December issue of The MagPi, which arrives in UK stores
today.  Russell, Rob and the team have been killing themselves putting this together, and we're very
pleased with how it's turned out.  The issue is jam-packed with everything you need to know about Zero,
including a heap of project ideas, and an interview with Mike Stimson, who designed the board.

If you're looking for cables to go with your free Zero, head over to the newly revamped Swag Store, where
we're offering a bundle comprising a mini-HDMI and a micro-USB adapter for just £4, or alternatively

Happy hacking!?

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27 Nov 09:46 2015

### Grobner fails to load on Maxima 5.35.1 with SBCL 1.2.8-1.el7


I've just installed Maxima from rpms on Redhat.  I've got the following error (below), which is a new one to
me.  I have looked for a solution to this, but can't find one.   I'll install another version (or from source)
but does anyone know what might have caused this?

Thanks
Chris

Maxima 5.35.1 http://maxima.sourceforge.net
using Lisp SBCL 1.2.8-1.el7
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.

Loading maxima-grobner $Revision: 1.6$ $Date: 2009-06-02 07:49:49$
;
; compilation unit aborted
;   caught 2 fatal ERROR conditions
-- an error. To debug this try: debugmode(true);
(%i2)

--

--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.

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26 Nov 22:04 2015

### jupyter maxima and sbcl


Robert Dodier
Maxima Jupyter works with maxima 5.37.3 compiled from source in sbcl
1.2.14, using ubuntu 15.10, 32 bits system.

uname -a
Linux username 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 23:32:28 UTC 2015
i686 i686 i686 GNU/Linux

I followed your instructions, it works, details follow:

1) install anaconda
2) git clone https://github.com/robert-dodier/maxima-jupyter
3) maxima code:
rlwrap maxima

parse_string("1");
:lisp (loop for system in (list :uiop  :asdf :sb-posix) do
:lisp (sb-ext:save-lisp-and-die "maxima-jupyter.core" :toplevel
'cl-jupyter:kernet-start :executable t)
quit();

4)  python3 ./install-maxima-jupyter.py

Finally to open a jupyter notebook:

5) jupyter notebook --Session.key="b''"

It works, thanks again.

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26 Nov 18:46 2015

### draw3d: hide portion of curve "behind" surface?

How do I hide the portion of the curve that is "behind" the surface?

draw3d(
color=black,
parametric(t,2*t^2,2,t,-4,4),
enhanced3d = false,
wired_surface=false,
color=red,
implicit(s,x,-3,3,y,0,15,z,1.6,2.4)
)$------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741551&iu=/4140 _______________________________________________ Maxima-discuss mailing list Maxima-discuss <at> lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/maxima-discuss  20 Nov 17:45 2015 ### Hilfe bei Maxima - Ausdrucken der Inputs ? Sehr geehrte Damen und Herren, Ich bräuchte Ihre Hilfe beim Drucken der Maxima Aufgaben, diese drucken bei mir (auch wenn ich alles bestätige) nur Outputs, aber ich möchte gerne die Inputs auch noch mit ausdrucken, da diese für die Schule wichtig sind! Ich habe Maxima bereits schon neu installiert komme aber nicht weiter. Auch meinen Lehrer habe ich gefragt, der meinte bei ihm würde alles funktionieren? Woran kann das liegen? Vielen Dank! Mit freundlichen Grüßen Daniel Zauner Deutschland, Bayern ------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741551&iu=/4140 _______________________________________________ Maxima-discuss mailing list Maxima-discuss <at> lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/maxima-discuss  26 Nov 06:59 2015 ### Re: speed of reading data files, was: installation problems  Found out what made the first two of my examples inefficient: Should have used "pop". Kind regards, Gunter. On 26.11.2015 06:37, Gunter Königsmann wrote: > >> * another thing is to rework the Maxima formatter and parser for >> greater speed and maybe memory use. This is potentially a big >> win but also more difficult. >> > Perhaps now my tries to benchmark different ways to output numbers > from maxima might be helpful after all. They show a big difference > between gcl and sbcl so I will try to convince my thunderbird to > add Camm as CC. Also I need some help what made the first two of my > test cases this slow - as I am convinced they should be quite > efficient when doing the same thing in lisp. > > What I did was try to save a million floating-point numbers on the > hard disk. I always compiled the function writetest before > executing it. The list was filled with the following contents: > > l:float(makelist(sin(i),i,1,1e6))$
>
>
> The test vectors and test results are:
>
> writetest(filename,list):=block([len,stream],
> stream:openw(filename), len::length(list), for i:1 thru len do (
> printf(stream,"~10$",first(list)), list:rest(list) ), > close(stream) ); > > gcl:5663.2 seconds/ sbcl: 862.1 seconds > > writetest(filename,list):=block([stream], stream:openw(filename), > while list # [] do ( printf(stream,"~10$",first(list)),
> list:rest(list) ), close(stream) );
>
> gcl:5621.1 seconds sbcl: 860.9140 seconds
>
> I was totally convinced that this is the most efficient way of
> traversing lists. What did I do wrong?
>
> writetest(filename,list):=block([stream,len],
> stream:openw(filename), len:length(list), for i:1 thru len do (
> printf(stream,"~10$",float(sin(i))) ), close(stream) ); > > gcl: 58.49 seconds, sbcl:31.51 seconds > > writetest(filename,l):=block([len], len:length(l), > with_stdout(filename,for i:1 thru len do disp(float(sin(i))) ) ); > > gcl:48.70 seconds, sbcl: 41.80 seconds > > writetest(filename,l):=block([strm,len], len:length(l), > strm:make_string_output_stream(), for i:1 thru len do > printf(strm,"~10$",float(sin(i)) ) );
>
> gcl: Cannot append to string (no complaints here: The string
> doesn't have a length that is within any realistic bounds), sbcl:
> 30.49 seconds.
>
> Kind regards,
>
> Gunter.
>

25 Nov 23:52 2015

### Latex formatting

Hello,

I am using wxMaxima.
Is it possible to change the default latex representation of multiplication (*) ?
Now it always produces \cdot which complicates notation.

Is it also possible to switch between \frac{d}{d x} and \frac{ \partial } { \partial x} in the Latex export of derivative forms?

best regards,

Dimiter
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25 Nov 23:38 2015

### Carminati-McLenaghan invariants with ctensor

I have an implementation of all of the Carminati-McLenaghan invariants now:
https://github.com/bcrowell/cm_invariants
Maybe this will be of some use to others who use Maxima for relativity. The results seem sensible on the
spacetimes I tried, although I need to find some published values for testing purposes.

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25 Nov 23:35 2015

### preventing names of algebraic symbols from conflicting with local variables?

Thanks, Richard Fateman and Stavros Macrakis, for the suggestions. Seems like it's clearly either a bug or a design feature, but anyway there are clearly some decent work-arounds.

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Gmane