Julia and Python in Astronomy: Better Together

Talk at "Python in Astronomy" workshop

Transcript

1. Kyle Barbary UC Berkeley / BIDS · github.com/kbarbary · @kylebarbary in Astronomy: Better Together &
2. “A fresh approach to technical computing”
3. I <3 I'm not going to tell you to stop using Python.
4. • Some things are impossible to “vectorize,” or just very awkward. • Possible to drop down to C but not easy • As library writers, having to write “array- oriented” APIs can be constraining. But...
5. The “two language” problem High-level dynamic language for rapid development (e.g., Python, R, Matlab, ...) Compiled language for performance-sensitive code (e.g., C, C++, Fortran) Interface code
6. Julia is fast... Microbenchmarks times relative to C (lower is better)
7. … but feels high-level.
8. … even at a very low level.
9. • Call C and Fortran directly with zero overhead, no wrappers • Zero-overhead quantities are possible: • Automatic differentiation is possible: A few more enticements:
10. A few more enticements: • Inspect native code: • Multithreading on its way (currently off by default)
11. Julia & Python: IJulia
12. Julia & Python: PyCall
13. wrap C libraries used in astropy
14. Other “registered” packages helgee/JPLEphemeris mweastwood/CasaCore emmt/OIFITS kbarbary/SkyCoords jzuhone/YT
15. Example: SkyCoords
16. Example: SkyCoords 10 0 10 1 10 2 10 3 10 4 10 5 10 6 jl_galactic jl_fk5j2000 jl_fk5j1975 py_galactic py_fk5j2000 py_fk5j1975 10 -8 10 -6 10 -4 10 -2 10 0
17. Rewriting all that Python? Typing is not the hard part. The hard part is figuring out what the code is supposed to do.
18. Python Cython C Python Cython C library My takeaways from Julia: C
19. Python Cython C Python Cython C library Julia PyPy + CFFI My takeaways from Julia: C
20. Takeaways from Julia: Modules
21. “SciPy… really was a distribution masquerading as a library. “... I made a mistake with SciPy because there was not good packaging in Python at the time.” Takeaways from Julia: Modules – Travis Oliphant
22. Thanks!
23. GitHub: @kbarbary Twitter: @kylebarbary Try it: juliabox.org More talking: julialang.org/learning Steven Johnson’s keynote at EuroSciPy 2014: “Crossing Language Barriers with Julia, SciPy, and IPython” • What's bad about Julia? • How can Python benefit from Julia? • Is anyone actually using Julia for astronomy? Sample Questions: