Ask Your Question

Volker Braun's profile - activity

2023-06-12 15:29:39 +0100 received badge  Nice Answer (source)
2022-06-02 17:44:18 +0100 received badge  Nice Answer (source)
2020-04-23 09:47:32 +0100 received badge  Good Answer (source)
2019-08-27 22:19:24 +0100 received badge  Nice Answer (source)
2019-02-10 18:43:37 +0100 received badge  Great Answer (source)
2018-11-23 03:11:02 +0100 received badge  Good Answer (source)
2018-09-03 13:20:13 +0100 received badge  Nice Answer (source)
2018-05-03 00:19:20 +0100 received badge  Nice Answer (source)
2018-03-13 11:54:43 +0100 received badge  Nice Answer (source)
2016-09-19 22:57:43 +0100 received badge  Good Answer (source)
2016-04-04 17:51:06 +0100 answered a question Is it possible to install sage 7.1 on OSX 10.11?

Fixed in the 7.2.beta0 OSX binaries

2016-04-04 17:46:37 +0100 commented question osx installation

Which command(s) are you calling?

Whats the backtrace of the RuntimeError

Why "during compilation", the dmg is already compiled. What are you doing?

2016-01-30 22:32:15 +0100 answered a question VM Virtualbox & sage-7.0.ova: how to start?

To switch between jupyter and the old SageNB you currently have to edit .xinitrc:

  • In the tree view, go to new -> terminal
  • type "nano .xinitrc"
  • edit according to the comments at the bottom
2016-01-30 22:31:43 +0100 answered a question Where is information passed on to var() stored?

Pynac/ginac tracks latex_name, so its a bit tricky to get at it.

The assumptions (like domain="real") are tracked in Sage:

sage: var('xt1', domain='real') 
xt1
sage: assumptions(xt1) 
[xt1 is real]
sage: forget(xt1, 'real') 
sage: assumptions(xt1) 
[] 
sage: assume(xt1 > 0)
2016-01-08 07:12:02 +0100 received badge  Nice Answer (source)
2016-01-07 23:42:41 +0100 commented answer Sage 6.10 not working again on MacOS

Correct, thats how it works

2016-01-07 18:42:09 +0100 commented answer Sage 6.10 not working again on MacOS

Just to be clear, you can only move / rename the SageMath folder before you start it for the first time. Once you started sage, you can neither move nor rename it. The "Updating various hardcoded paths" message is incorrect and does not do it.

2016-01-07 15:32:32 +0100 answered a question Sage 6.10 not working again on MacOS

How did you manage to get there? You should

  • Open the DMG (or tar.bz2)
  • Drag the SageMath folder / app to where you want it to be (possibly rename it)
  • Start sage

This will then automatically patch paths in binaries. Once it is installed you cannot move the installation any more.

2015-09-30 23:55:38 +0100 received badge  Nice Answer (source)
2015-02-06 11:01:39 +0100 received badge  Great Answer (source)
2015-01-08 10:47:23 +0100 received badge  Good Answer (source)
2014-12-11 16:17:50 +0100 received badge  Nice Answer (source)
2014-11-19 16:13:02 +0100 answered a question gcc cython compilation error in OSX 10.10

If you get the "found MacPorts in /opt/local/bin/port. Either: (1) rename /opt/local and /sw, or (2) change PATH and DYLD_LIBRARY_PATH (Once Sage is built, you can restore them.)" error then just do that.

2014-11-11 14:44:12 +0100 answered a question Plotting planes

Yet another solution is to define the planes as (non-compact) polyhedra:

sage: P_prime = Polyhedron(eqns=[(1, -1,2,1)])
sage: P_prime.Hrepresentation() 
(An equation (1, -2, -1) x - 1 == 0,)
sage: P_prime.Vrepresentation()
(A line in the direction (0, 1, -2),
 A line in the direction (1, 0, 1),
 A vertex at (0, 0, -1))
sage: P_prime.plot()
2014-11-09 13:17:22 +0100 answered a question sage notebook will not start after switching to Mavericks / Yosemite

The 10.9 binary will work on 10.10. You need sage-6.4 (-rc) to compile anything on Yosemite, though.

Your issue is a corrupted ~/.sage/sage_notebook.sagenb/users.pickle, rename it and try again.

2014-11-09 13:12:26 +0100 answered a question Virtualbox and Chromium

X is launched from /home/sage/.bash_profile, which runs .xinitrc, which starts chromium in kiosk mode. You can change either of them (I would suggest to make a VM snapshot first).

Having said that, you'll probably be better off with doing a full Linux installation in a new virtual machine and then compiling Sage yourself. Its easy enough...

2014-11-09 13:01:53 +0100 answered a question Trouble installing nauty on Mac OS X 10.10

You need Sage-6.4 (-rc) to compile Sage or third party packages on OSX 10.10 Yosemite

2014-10-30 22:10:40 +0100 received badge  Nice Answer (source)
2014-10-03 12:04:12 +0100 answered a question The boundary of an implicit_plot3d are jittery.

Neat plot! To some extent it is unavoidable, if you have a tube at an odd angle in 3-d then the plot sample points will not line up in the direction of the tube. So no matter how you join the vertices into triangles, it'll always be jagged. If you need visual perfection then you probably have to use tachyon and crank up plot_points to have triangles that are only a few pixels wide.

2014-09-24 12:58:40 +0100 answered a question Create new structure class and define its element

The rule in Sage is to always use A.element_class, and never the original element class MyElement. In fact, they are not the same:

sage: a = A.element_class(A,{(1,):1})
sage: a
x
sage: type(a)
<class '__main__.MyAlgebra_with_category.element_class'>

This is how the category framework operates. Polynomial algebra is also optimized a lot, so its not the easiest part in Sage to understand (sorry). To construct the correct kind of polynomials you also need to override

class MyAlgebra(sage.structure.unique_representation.UniqueRepresentation, sage.rings.polynomial.multi_polynomial_ring.MPolynomialRing_polydict):
         Element=MyElement
         def _poly_class(self):
             return self.element_class
2014-09-21 19:47:00 +0100 commented answer Adventures trying to build 6.3 on cygwin

Are you using Windows 32 bit? I've fiddled around with it for days until I convinced myself that it'll never work due to address space changes between different runs. Windows 64-bit (even with 32-bit userspace) has a much better chance. On a related note, what is this Windows dominance you are talking about? The accountants and secretaries of the world use Windows, but it has negligible market share in the scientific computing area. If you are serious about computing learn unix asap, you'll thank me later.

2014-09-21 19:38:44 +0100 answered a question What's the best way to access sage from a C program?

I would turn it around, instead of controlling Sage from within your C++ program make Sage/IPython your user interface. Then call into your C++ code for whatever you want it to do quickly. Will be a much nicer interface than calling your binary with different arguments.

Typically C/C++ code does some fast numerics after you have done some symbolic preprocessing, so usually you don't need to call back into Python then. But you definitely can using the Python C API (tedious), or by linking against Cython module and calling cdef functions, or boost:python.

Simple example of a C++ lattice simulation code controlled from the Sage commandline: https://github.com/vbraun/lattice_phi4

2014-09-21 19:27:30 +0100 answered a question How do I modify the 6.3 virtual to remove the login page in windows?
2014-09-21 19:13:01 +0100 commented answer Why does Sage offer unusable SciPy?

Sage is also a system for doing research, that includes comparing different implementations. A lot of work went into picking suitable defaults. Why shouldn't we expose the other implementations, too? Maybe SciPy improves in some future version...

2014-09-12 09:06:44 +0100 received badge  Nice Answer (source)
2014-08-21 19:04:01 +0100 received badge  Nice Answer (source)
2014-08-06 18:42:22 +0100 received badge  Good Answer (source)
2014-08-05 10:15:31 +0100 received badge  Nice Answer (source)
2014-08-04 18:00:51 +0100 answered a question enumerate integer points in a polytope

This is probably out of reach for any "generic" point counting:

sage: p
A 14-dimensional polyhedron in QQ^19 defined as the convex hull of 144716 vertices

You can probably use the specifics of your problem since its just a limited range in each variable. E.g. try to find a solution mod 3 and then try to lift it to ZZ.

2014-08-04 03:58:04 +0100 received badge  Good Answer (source)
2014-08-01 21:13:23 +0100 received badge  Nice Answer (source)
2014-07-29 04:49:53 +0100 commented answer Git-Trac command setup

Another workaround would be to not use ssl, but the unencripted git protocol: "git clone git://github.com/sagemath/git-trac-command.git"

2014-07-10 17:32:34 +0100 commented answer bug pdflatex sage-6.2 ?

You can install anything in the virtual appliance, see http://wiki.sagemath.org/SageAppliance. Open a root shell and run "yum install texlive"

2014-07-09 17:38:14 +0100 commented answer projection_direction broken for polytopes?
2014-07-08 23:37:44 +0100 answered a question bug pdflatex sage-6.2 ?

(PDF)Latex is not part of Sage, but obviously some functionality depends on it. Install your distribution's LaTeX.

2014-07-08 23:30:58 +0100 commented answer Sage 4.6 not compiling on OpenSuse 11.3 (x86_64)

Then why did you resurrect it? ;-)

2014-07-08 21:42:40 +0100 received badge  Nice Answer (source)
2014-07-08 18:25:40 +0100 answered a question projection_direction broken for polytopes?

This works for me:

sage: P8.schlegel_projection([2,5,11,17]).show()

The polyhedron show() method does not support a projection_direction optional argument. The reference manual link that you gave points to the internally-used Projection class, not the Polyhedron class which is the user interface.

2014-02-03 16:56:03 +0100 answered a question frozenset error when plotting polytopes: bug?

Its basically this bug: http://trac.sagemath.org/ticket/10046

We don't have an arbitrary precision polytopes, so sooner or later numerical errors in floating point numbers will give you the wrong answer.