Mailman 3 February 2006 - SciPy-User

numpy weave problems resolved
by Christian Kristukat Feb. 18, 2006

Feb. 18, 2006

Hi, some weeks ago I reported problems with the new numpy/weave when using the automatic type conversion. I finally boiled it down to some few lines which demonstrate the problem: import scipy.weave as weave from scipy.weave import converters import numpy code = """ double c = a2(ind(2),0); """ ind = numpy.array([0,3,2]) #ind = numpy.array([0,3,2],'i') a2 = numpy.arange(9) a2 = numpy.reshape(a2,(3,3)) weave.inline(code, ['a2','ind'], type_converters=converters.blitz) I found out that you cannot use the elements of an integer array to index another array if the former is not explicitly set to dtype='i'. Thus, if you uncomment the second array intialization above, the code compiles and runs. Once compiled, however, you can remove the dtype argument again. Apparently the types are compatible during runtime, but the compiler is checking compatibility more strictly. I'd prefer a relaxed type checking, if possible. Regards, Christian

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Cluster of workstation
by Hugo Gamboa Feb. 18, 2006

Feb. 18, 2006

Hi to all, I'm starting to need a small cluster to divide some of my computing tasks. What is the best direction to follow? pyMPI, cow.py, seppo with pyro? I've started to look at cow.py that presented a very simple approach, aparently well integrated with scipy, but I falied to start the cluster. Is cow abandoned? Thanks for your support. Hugo Gamboa

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casting complex numbers
by Ryan Krauss Feb. 18, 2006

Feb. 18, 2006

Is there a way to make python return a complex number number instead of nan when taking the sqrt of a negative float? I have an automatically generated function based on Maxima symbolic output that is giving bad output because of this. Basically, part of the symoblic expression includes sqrt(-s**2*x) where s is complex and this expression would evaluate nicely in python. For whatever reason, Maxima prefers to output this expression as sqrt(-x)*s, which would also evaluate correctly if sqrt(-x) gave 1.0j*sqrt(x), but since x is a float it is returning nan. I am hoping for flag similar to from __future__ import division instead of having to declare all my variables as complex. Thanks, Ryan

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fft numerical precision
by Darren Dale Feb. 17, 2006

Feb. 17, 2006

I am running into problems related, I think, to numerical precision of fast Fourier transforms. If I Fourier transform a gaussian distribution: absolute(fft(stats.norm.pdf(linspace(-10,10,512), loc=0, scale=1))) I find a floor of about 1e-16. Does anyone know of a way to improve the precision? Thanks, Darren

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Re: [SciPy-user] [Numpy-discussion] ANN: Python Enthought Edition Version 0.9.2 Released
by Travis N. Vaught Feb. 17, 2006

Feb. 17, 2006

Arnd Baecker wrote: > On Thu, 16 Feb 2006, Travis N. Vaught wrote: > > >> Enthought is pleased to announce the release of Python Enthought Edition >> Version 0.9.2 (http://code.enthought.com/enthon/) -- a python >> distribution for Windows. This is a kitchen-sink-included Python >> distribution including the following packages/tools out of the box: >> >> Numeric 24.2 >> SciPy 0.3.3 >> IPython 0.6.15 >> Enthought Tool Suite 1.0.2 >> wxPython 2.6.1.0 >> PIL 1.1.4 >> mingw 20030504-1 >> f2py 2.45.241_1926 >> MayaVi 1.5 >> Scientific Python 2.4.5 >> VTK 4.4 >> and many more... >> > > Brilliant - many thanks for the effort! > > I was just about to ask for the plans about numpy/scipy, > but the changelog at > http://code.enthought.com/release/changelog-enthon0.9.2.shtml > shows quite a bit of activity in this direction! > > Do you have an estimate about when a numpy/scipy version > of the Enthought Edition might happen? > > Many thanks, > > Arnd > It's a bit difficult to say with much accuracy, so I'll be transparent but imprecise. Our release of Enthon versions typically tracks the state of the platform we are using for the custom software development we do to pay the bills. Thus, our current project code typically has to be ported to build and run on a cobbled-together build of the newer versions before we do a release. I realize this is a drag on the release schedule for Enthon, but it's how we allocate resources to the builds. Enough excuses, though--we are working on the migration of our project code now (Pearu Peterson) and I expect in weeks (rather than months) we'll have an Enthon release candidate with Python 2.4.2, and the latest SciPy and NumPy on Windows. Robert Kern is already working on a project that is based on this tool chain, so the wedge is in place. Thanks for the interest! (and sorry for the cross-post) Travis

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Release of NumPy 0.9.5
by Travis Oliphant Feb. 17, 2006

Feb. 17, 2006

I'm pleased to announce the release of NumPy 0.9.5 The release notes and download site can be found at http://www.scipy.org Best regards, -Travis Oliphant

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Trace of a sparse matrix ?
by Nils Wagner Feb. 16, 2006

Feb. 16, 2006

Hi all, Is it possible to compute the trace of a sparse matrix say A without detouring spur=trace(A.todense()) ? Nils

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Installation on cygwin
by Jose Luis Gomez Dans Feb. 16, 2006

Feb. 16, 2006

Hi! I am trying to install Scipy (latest tarball from scipy.org) on cygwin (updated to today). As I understand it, I need to first install Numpy, and then Scipy. I can't install numpy (the ufuncs directory has a myriad of undefined symbols), and I see on the mailing list that a few other people hit the same problem. Has anyone successfully compiled numpy+scipy on cygwin? Does it make sense to use an older version of either? Many thanks! jose -- DSL-Aktion wegen gro�er Nachfrage bis 28.2.2006 verl�ngert: GMX DSL-Flatrate 1 Jahr kostenlos* http://www.gmx.net/de/go/dsl

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Dense matrices versus sparse matrices
by Nils Wagner Feb. 16, 2006

Feb. 16, 2006

Hi all, I am going to solve l a r g e Sylvester equations A X + X B = C and I should use sparse matrices instead of dense matrices. However, I started with a dense version (ggsl-dense.py) and the results are very promising. But if I use the sparse version (ggsl-sparse.py) the results are different (floating point numbers differ in the last 7 digits). I guess that something went wrong during the transition process. Who can help me with this task ? The codes are available upon request. :-) Cheers, Nils

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Numpy for Matlab users
by Nils Wagner Feb. 16, 2006

Feb. 16, 2006

Hi all, I am converting a Matlab code into a numpy/scipy code. How can I translate H(k+1,:) = [ ] into numpy ? Nils

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