Wednesday, May 30. 2012
There are not too many examples of sucessful open-source projects in scientific software. One of them is Sage, a mathematical software system aimed at creating a viable free open-source alternative to Magma, Maple, Mathematica and Matlab.
In a recent interview, the developers of Sage gave the following answer to the question Why do you consider free/libre open source software important for the advancement of your field?
[...] When we contribute to mathematics, it is important to contribute both the results and the methods. When software plays an essential role in research, this is a valuable part of the public contribution. If other mathematicians can’t learn how it works, modify it, and use it for new purposes, then there is a serious loss of value.
Naturally, some of this discussion applies to Madagascar as well.
For integration of Madagascar and Sage, one can use the Python interface.
Wednesday, May 16. 2012
The following Madagascar-related meetings are taking place this summer.
Workshop 16 at the 2012 EAGE Annul Meeting in Copenhagen, Denmark, is titled Open-source E+P Software - Six Years Later and scheduled on Friday, June 8. The title refers to an analogous workshop in Vienna in 2006, where Madagascar was first publicly announced. The workshop is organized by Joseph Dellinger, Karl Schleicher, Helene Huck, and Tariq Alkhalifah and features an extensive program with multiple presentations.
This year's Madagascar School and Workshop will take place in Austin, Texas, on Friday-Saturday July 20-21. Please reserve the date and wait for the announcement of the program and registration details.
Thursday, May 3. 2012
A new paper is added to the collection of reproducible documents:
Non-hyperbolic common reflection surface
Tuesday, May 1. 2012
sfderiv applies the first derivative filter.
The algorithm implemented in this program is described in the paper
Pei, S.-C., and P.-H. Wang, 2001, Closed-form design of maximally flat FIR Hilbert transformers, differentiators, and fractional delayers by power series expansion: IEEE Trans. on Circuits and Systems, v. 48, No. 4, 389-398.
It is based on the Taylor expansion of the inverse sine function
which turns into an expansion of the ideal derivative filter into a chain of digital filters.
The order= parameter controls the order of the expansion and the accuracy-efficiency trade-off. The following example from rsf/rsf/sfderiv shows the frequency responses and the impulse responses for differentiators of different orders
An alternative is sfigrad, which implements a simple first-order derivative. igrad is more efficient and adequate when computing derivatives of smooth functions.
Previous programs of the month:
The paper Performance Evaluation of Open Source Seismic Data Processing Packages by Izzatdin A. Aziz, Andrzej M. Goscinski, and Michael M. Hobbs from Deakin University was presented at the 11th International Conference on Algorithms and Architectures for Parallel Processing (ICA3PP 2011).
"The goal in this paper was to demonstrate the capability of open source packages,
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