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Hybrid Elimination Improvements #1575

Merged
merged 17 commits into from
Jul 19, 2023
Merged

Hybrid Elimination Improvements #1575

merged 17 commits into from
Jul 19, 2023

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varunagrawal
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@varunagrawal varunagrawal commented Jul 12, 2023

  • Override apply with UnaryAssignment for DecisionTreeFactor.
  • Improve discrete elimination by eliminating the joint distribution and re-segregating back into original conditionals.
  • Make hybrid code use common parent DiscreteFactor where applicable.
  • Update the eliminate method to check the factors as mentioned in @dellaert's TODO.
  • Templetize methods in Switching.h to remove duplication.

@varunagrawal varunagrawal self-assigned this Jul 12, 2023
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I changed the way we prune the discrete probabilities by pruning the joint distribution rather than the conditionals. This gives a 3x speedup. Maybe we should be pruning before discrete-only elimination.

Before

Number of timesteps: K = 16

-Total: 0 CPU (0 times, 0 wall, 0.65 children, min: 0 max: 0)
|   -SmootherEstimation: 3.65 CPU (1 times, 3.70242 wall, 0.65 children, min: 0 max: 0)
|   |   -SmootherUpdate: 3.63 CPU (15 times, 3.67252 wall, 0.65 children, min: 0 max: 0)
|   |   |   -assembleGraphTree: 0.01 CPU (30 times, 0.00976 wall, 0.01 children, min: 0 max: 0)
|   |   |   -hybrid continuous eliminate: 0 CPU (168 times, 0.006431 wall, 0 children, min: 0 max: 0)
|   |   |   -HybridBayesNet PruneDiscreteConditionals: 0.64 CPU (15 times, 0.640958 wall, 0.64 children, min: 0 max: 0)
|   |   |   -HybridBayesNet UpdateDiscreteConditionals: 2.8 CPU (15 times, 2.84436 wall, 0 children, min: 0 max: 0)
|   |   |   |   -HybridBayesNet MakeConditional: 0 CPU (120 times, 0.001385 wall, 0 children, min: 0 max: 0)
|   |   |   -HybridBayesNet PruneMixtures: 0 CPU (15 times, 0.009233 wall, 0 children, min: 0 max: 0)

After

Number of timesteps: K = 16

-Total: 0 CPU (0 times, 0 wall, 0.71 children, min: 0 max: 0)
|   -SmootherEstimation: 0.91 CPU (1 times, 0.904348 wall, 0.71 children, min: 0 max: 0)
|   |   -SmootherUpdate: 0.88 CPU (15 times, 0.882961 wall, 0.71 children, min: 0 max: 0)
|   |   |   -assembleGraphTree: 0 CPU (30 times, 0.009388 wall, 0 children, min: 0 max: 0)
|   |   |   -hybrid continuous eliminate: 0 CPU (168 times, 0.004795 wall, 0 children, min: 0 max: 0)
|   |   |   -HybridBayesNet PruneDiscreteConditionals: 0.64 CPU (15 times, 0.632673 wall, 0.64 children, min: 0 max: 0)
|   |   |   -HybridBayesNet UpdateDiscreteConditionals: 0.07 CPU (15 times, 0.071286 wall, 0.07 children, min: 0 max: 0)
|   |   |   -HybridBayesNet PruneMixtures: 0 CPU (15 times, 0.00871 wall, 0 children, min: 0 max: 0

@dellaert
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I changed the way we prune the discrete probabilities by pruning the joint distribution rather than the conditionals. This gives a 3x speedup. Maybe we should be pruning before discrete-only elimination.

Does this PR make both these changes? I'd prefer to review a PR that just does the tablefactor and shows the speedup...

@varunagrawal varunagrawal changed the title TableFactor for Hybrid Elimination Hybrid Elimination Improvements Jul 16, 2023
@varunagrawal
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I changed the way we prune the discrete probabilities by pruning the joint distribution rather than the conditionals. This gives a 3x speedup. Maybe we should be pruning before discrete-only elimination.

Does this PR make both these changes? I'd prefer to review a PR that just does the tablefactor and shows the speedup...

This PR only updates the discrete elimination to prune the joint distribution. TableFactor is not yet used, and will come in a subsequent PR. :)

Updated PR description to reflect the changes happening here.

@dellaert
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I'd still like to request to split into TableFactor related changes and other, and PR straight to develop? Otherwise the base branch will become an un-reviewable kitchen-sink PR. PS CI seems to fail, so splitting might help there as well.

@varunagrawal
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In that case I'm going to have to do some cherry picking and force pushing.

@varunagrawal
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I'd still like to request to split into TableFactor related changes and other, and PR straight to develop? Otherwise the base branch will become an un-reviewable kitchen-sink PR. PS CI seems to fail, so splitting might help there as well.

It won't be a kitchen sink PR if we merge in the parent PRs first.

Base automatically changed from hybrid-tablefactor to develop July 17, 2023 15:54
@varunagrawal
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@dellaert I split the changes to TableFactor into #1580.

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Some comments. This PR changed too many things at once to be sure of anything, though.

@@ -299,6 +299,42 @@ namespace gtsam {
/// Return the number of leaves in the tree.
size_t nrLeaves() const;

/**
* @brief This is a convenience function which returns the total number of
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Spelling. And why are we adding it ? And why is the implementation recursive.
I would just as well delete it unless it has a purpose.

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I'm a bit lost on which word is misspelled. The purpose is to help with testing and ensure correctness as a convenience method.

@@ -231,7 +231,7 @@ TEST(HybridBayesNet, Pruning) {
auto prunedTree = prunedBayesNet.evaluate(delta.continuous());

// Regression test on pruned logProbability tree
std::vector<double> pruned_leaves = {0.0, 20.346113, 0.0, 19.738098};
std::vector<double> pruned_leaves = {0.0, 32.713418, 0.0, 31.735823};
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What's happening here? Why are regressions changing ?

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The decision tree is normalizing the values based on the introduced zeros from pruning. Since I changed the way we're pruning (on the joint rather than the conditionals), the normalizing factor has changed.

double density = exp(logProbability);
EXPECT_DOUBLES_EQUAL(density, actualTree(discrete_values), 1e-9);
EXPECT_DOUBLES_EQUAL(density,
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This was not a regression but suddenly there is an arbitrary mult factor here?

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That is the multiplicative factor for the different normalization constant.

@@ -63,8 +63,8 @@ TEST(MixtureFactor, Printing) {
R"(Hybrid [x1 x2; 1]
MixtureFactor
Choice(1)
0 Leaf Nonlinear factor on 2 keys
1 Leaf Nonlinear factor on 2 keys
0 Leaf [1]Nonlinear factor on 2 keys
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spacing is weird in this case.

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Done

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OK, merge this at will :-)

@varunagrawal varunagrawal merged commit ba7c077 into develop Jul 19, 2023
@varunagrawal varunagrawal deleted the hybrid-tablefactor-2 branch July 19, 2023 10:42
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2 participants