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Make Sampler a field of DefaultContext (renamed to SamplingContext) #80

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mohamed82008 opened this issue Apr 20, 2020 · 3 comments
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Make Sampler a field of DefaultContext (renamed to SamplingContext) #80

mohamed82008 opened this issue Apr 20, 2020 · 3 comments

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@mohamed82008
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mohamed82008 commented Apr 20, 2020 •
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Currently we have 2 arguments for changing the behavior of assume and observe, context and sampler. I think:

  1. Sampler belongs in a field in DefaultContext, perhaps renaming it to SamplingContext,
  2. SampleFromPrior should always overwrite the values in VarInfo much like SampleFromUniform in Fix SampleFromUniform #78, and
  3. ComputeLogpContext can be another context which encompasses LikelihoodContext, PriorContext and the current behavior of DefaultContext with SampleFromPrior.

I always found it confusing the SampleFromPrior doesn't actually sample anything if VarInfo already has values.
This was referenced Apr 13, 2021
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bors bot pushed a commit that referenced this issue Apr 18, 2021
@devmotion
Fix initialization of parameters for algorithms that use `SampleFromU…
7c8edab 
…niform` (#232)

This PR is a quick fix for TuringLang/Turing.jl#1563 and TuringLang/Turing.jl#1588.

As explained in TuringLang/Turing.jl#1588 (comment), the problem is that currently `SampleFromUniform` always resamples variables in every run, and hence also initial parameters provided by users are resampled in https://github.com/TuringLang/DynamicPPL.jl/blob/9d4137eb33e83f34c484bf78f9a57f828b3c92a0/src/sampler.jl#L80.

As mentioned in TuringLang/Turing.jl#1588 (comment), a better long term solution would be to fix this inconsistency and use dedicated evaluation and sampling contexts, as suggested in #80.
@torfjelde torfjelde mentioned this issue May 25, 2021
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@yebai
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yebai commented Dec 19, 2024

@penelopeysm is this now fixed?

@penelopeysm
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Totally missed this! But yes, (1) and (3) are fixed.

SampleFromPrior is still misleadingly named as it is a no-op if variables already exist in VarInfo. I have found this v v confusing myself too. But I think we can open a separate issue for this

@penelopeysm
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#859

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@yebai @mohamed82008 @penelopeysm