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BUILDING THE SOFTWARE INFRASTRUCTURE FOR ASTROPHYSICS by Dan Foreman-Mackey

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who am I? / / what’ve I been up to? 1

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7 [1] solving Hard™ data analysis problems [2] enabling and empowering astrophysicists

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implementation.

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data = > physics

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open source software for astrophysics 2

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why?

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credit: Adrian Price-Whelan / / data: SAO/NASA ADS

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my open source contributions 3

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gaussian processes 4

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p(data|physics)

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data ~ N(model; noise)

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°0.6 °0.3 0.0 0.3 0.6 raw [ppt] 0 5 10 15 20 25 time [days] °0.30 °0.15 0.00 de-trended [ppt] N = 1000 reference: DFM+ (2017)

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°0.6 °0.3 0.0 0.3 0.6 raw [ppt] 0 5 10 15 20 25 time [days] °0.30 °0.15 0.00 de-trended [ppt] N = 1000 reference: DFM+ (2017)

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data ~ N(model; noise)

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data ~ N(model; noise)

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so. why not?

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data ~ N(model; noise)

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reference: Ambikasaran, DFM+ (2015)

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reference: Ambikasaran, DFM+ (2015)

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reference: DFM, Agol, Ambikasaran, Angus (2017); DFM (2018); DFM, Luger, et al. (2021)

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reference: Gordon, Agol, DFM (2020)

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what’s next?

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credit: Quang Tran

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reference: Luger, DFM, Hedges (2021)

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probabilistic inference 5

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p(data|physics)

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have: physics = > data

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want: data = > physics

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integral of the form f(physics) p(physics|data) dphysics

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number of parameters patience required a few tenish not outrageously many reference: DFM (priv. comm.)

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number of parameters patience required emcee a few tenish not outrageously many reference: DFM (priv. comm.)

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number of parameters patience required emcee a few tenish not outrageously many how things should be reference: DFM (priv. comm.)

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gradients!

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dp(data|physics) / dphysics

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automatic differentiation aka “backpropagation”

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your model is just code

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apply the chain rule

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apply the chain rule over and over again . . .

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sounds silly?

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it's not! (mostly)

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what’s next?

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jax.readthedocs.io

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my approach to open source 6

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[1] don’t underestimate users [2] build libraries, not (just) scripts [3] teach by example

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bringing open source practices to research more generally

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what’s next? 7

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7 [1] inference with stochastic or intractable models [2] what can we do to better support open source in astrophysics

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7

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7 credit: Adrian Price-Whelan

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many fundamental software packages have a shockingly small number of maintainers.

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a selection of some* CCA-supported software: * my apologies for neglecting your favorites!

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BUILDING THE SOFTWARE INFRASTRUCTURE FOR ASTROPHYSICS @ CCA