Objective functions should not compute the sensitivities upon `set_up`
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- Dominant language
- C++
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- Avg merge
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Description
Utilities such as OSSPS,compute_sqrt_Hessian_row_sum, demo4 and demo5 utilise Poisson objective functions but do not need the system matrix sensitivities (A^T 1), yet they are computed. This additional and unnessicery computation slows down these utilities.
Perhaps with the changes being made in #893, the sensitivity do not need to be computed during set_up. Prior to this PR, the sensitivities were used in the subset-gradient computation, grad = A_m^T [ y_m/ (A_m(x) + b_m) ] - sensitivity_m making this suggestion infeasable.
When #893 is merged, it could be that the sensitivities are only computed if objective_function.get_subset_sensitivity(subset_num); is called.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing the objective-function setup and the changes proposed in issue #893. Check the OSSPS, compute_sqrt_Hessian_row_sum, demo4, and demo5 call paths, then verify that sensitivities are computed only when get_subset_sensitivity(subset_num) is called and that subset-gradient behavior remains correct.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- performance
- Issue type
- Refactor
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100