Improving Parameter Estimation Efficiency for Advanced Detector Data Analysis of Compact Binary...

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IntroductionParallelization

Variable ResolutionSummary

Improving Parameter Estimation Efficiencyfor Advanced Detector Data Analysis

of Compact Binary Coalescence

J. M. Bell1 2 J. Veitch2 3

1Millsaps College

2Gravitational PhysicsNIKHEF

3Department of PhysicsUniversity of Birmingham Physics

University of Florida IREU in Gravitational Physics

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 1 / 20

IntroductionParallelization

Variable ResolutionSummary

Gravitational WavesParameter EstimationNested SamplingMotivation

Gravitational Waves

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 2 / 20

IntroductionParallelization

Variable ResolutionSummary

Gravitational WavesParameter EstimationNested SamplingMotivation

Gravitational WavesFrom Compact Binary Coalescence

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 3 / 20

IntroductionParallelization

Variable ResolutionSummary

Gravitational WavesParameter EstimationNested SamplingMotivation

Parameter EstimationDoing the Physics!

I 2 MassesI TimeI Sky positionI DistanceI 2 Orientation AnglesI 6 Spin Components

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IntroductionParallelization

Variable ResolutionSummary

Gravitational WavesParameter EstimationNested SamplingMotivation

Parameter EstimationA Bayesian Algorithm

Nested Sampling

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IntroductionParallelization

Variable ResolutionSummary

Gravitational WavesParameter EstimationNested SamplingMotivation

Motivation

I The Problem:Data analysis via Nested Sampling takes time

I The Solution:Improving the efficiency of Nested Sampling

I ParallelizationI Multiple Bandwidth Analysis

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 6 / 20

IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Parallelization

I Nested sampling converges on the maximum likelihoodI faster with the use of fewer live pointsI more accurately with the use of more live points

I Goals:I to reduce overall computational time while maintaining

sufficient accuracyI to optimize this procedure by finding the most effective

range of live points.

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

ParallelizationMethod

1 Run multiple instances in parallel with different NliveI 1 @ 1024I 2 @ 512I 4 @ 256

...I 64 @ 16

2 Recombine the results weighted by their parameterestimates

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 8 / 20

IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Parallelization ResultsChirp Mass Cumulative Distributions

Factors of 1024 Factors of 256

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Parallelization ResultsAccuracy and Efficiency

Posterior Samples

Nlive

Computational Time (s)

Nlive

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 10 / 20

IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

ParallelizationConclusions

I Parallelization can reduce computational time arbitrarilyI Reducing Nlive by 50% returns 75% of the posterior

samples

I The optimal range for Nlive is 200 to 256I The total Nlive across instances should be over 1000

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Switching Gears

Time Domain to Frequency DomainF vs. T function

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Multi-bandwidth Analysis

I Resolution is related to the number of samples in aninterval

I high resolution is redundantI low resolution is efficient

I Plan:I to downsample the frequency domain waveform according

to an optimized function based on the Nyquist timeI Goals:

I to exploit the monochromatic, low frequency nature of theearly waveform

I to focus computational resources on the more complexregion near the merger

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Variable Resolution MethodDetermining the Sampling Rate

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Variable Resolution MethodA Broken Waveform

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Variable Resolution ResultsAccuracy

Bands % Match1 99.99972 99.95413 99.75894 99.53515 99.3865

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Variable Resolution ResultsEfficiency

Bands d+hh:mm:ss1 ≈ 4+09:00:002 3+16:28:543 2+23:22:124 2+18:19:395 2+17:30:19

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IntroductionParallelization

Variable ResolutionSummary

OverviewMethodResultsConclusions

Variable Resolution Conclusions

I Variable Resolution analyses are feasible for parameterestimation

I A computation requiring roughly 50% of the time retainsover 99% of the accuracy

I Other methods of interpolation could lead to greateraccuracy

I Further work needed to eliminate remaining issues

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IntroductionParallelization

Variable ResolutionSummary

Summary and Outlook

Summary and Outlook

I Parallelization and Variable Resolution are viable means ofreducing computational time

I What lies ahead?I Optimization of the multiband algorithmI Simultaneous testing of both approachesI Implementation in the time domain

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IntroductionParallelization

Variable ResolutionSummary

Summary and Outlook

J.M. Bell, J. Veitch Improving CBC Parameter Estimation Efficiency 20 / 20

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