update doc string in BayesTreeMarginalizationHelper.h
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@ -37,53 +37,33 @@ public:
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using Clique = typename BayesTree::Clique;
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using sharedClique = typename BayesTree::sharedClique;
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/** Get the additional keys that need to be re-eliminated when marginalizing
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/** Get the additional keys that need reelimination when marginalizing
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* the variables in @p marginalizableKeys from the Bayes tree @p bayesTree.
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*
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* @param[in] bayesTree The Bayes tree to be marginalized.
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* @param[in] bayesTree The Bayes tree.
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* @param[in] marginalizableKeys The keys to be marginalized.
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*
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*
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* When marginalizing a variable @f$ \theta @f$ in a Bayes tree, some nodes
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* may need to be re-eliminated. The variable to be marginalized should be
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* eliminated first.
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* When marginalizing a variable @f$ \theta @f$ from a Bayes tree, some
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* nodes may need reelimination to ensure the variables to marginalize
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* be eliminated first.
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*
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* 1. If @f$ \theta @f$ is already in a leaf node @f$ L @f$, and all other
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* frontal variables within @f$ L @f$ are to be marginalized, then this
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* node does not need to be re-eliminated; the entire node can be directly
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* marginalized.
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* We should consider two cases:
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*
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* 2. If @f$ \theta @f$ is in a leaf node @f$ L @f$, but @f$ L @f$ contains
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* other frontal variables that do not need to be marginalized:
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* a. If all other non-marginalized frontal variables are listed after
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* @f$ \theta @f$ (each node contains a frontal list, with variables to
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* be eliminated earlier in the list), then node @f$ L @f$ does not
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* need to be re-eliminated.
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* b. Otherwise, if there are non-marginalized nodes listed before
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* @f$ \theta @f$, then node @f$ L @f$ needs to be re-eliminated, and
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* correspondingly, all nodes between @f$ L @f$ and the root need to be
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* re-eliminated.
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* 1. If a child node relies on @f$ \theta @f$ (i.e., @f$ \theta @f$
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* is a parent / separator of the node), then the frontal
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* variables of the child node need to be reeliminated. In
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* addition, all the descendants of the child node also need to
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* be reeliminated.
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*
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* 3. If @f$ \theta @f$ is in an intermediate node @f$ M @f$ (non-leaf node),
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* but none of @f$ M @f$'s child nodes depend on variable @f$ \theta @f$
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* (they only depend on other variables within @f$ M @f$), then during the
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* process of marginalizing @f$ \theta @f$, @f$ M @f$ can be treated as a
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* leaf node, and @f$ M @f$ should be processed following the same
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* approach as for leaf nodes.
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* 2. If other frontal variables in the same node with @f$ \theta @f$
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* are in front of @f$ \theta @f$ but not to be marginalized, then
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* these variables also need to be reeliminated.
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*
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* In this case, the original elimination of @f$ \theta @f$ does not
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* depend on the elimination results of variables in the child nodes.
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* These variables were eliminated before @f$ \theta @f$ in the original
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* Bayes tree, and after reelimination they will be eliminated after
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* @f$ \theta @f$ so that @f$ \theta @f$ can be marginalized safely.
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*
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* 4. If @f$ \theta @f$ is in an intermediate node @f$ M @f$ (non-leaf node),
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* and there exist child nodes that depend on variable @f$ \theta @f$,
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* then not only does node @f$ M @f$ need to be re-eliminated, but all
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* child nodes dependent on @f$ \theta @f$, including descendant nodes
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* recursively dependent on @f$ \theta @f$, also need to be re-eliminated.
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*
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* The frontal variables in child nodes were originally eliminated before
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* @f$ \theta @f$ and their elimination results are relied upon by
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* @f$ \theta @f$'s elimination. When re-eliminating, they should be
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* eliminated after @f$ \theta @f$.
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*/
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static void gatherAdditionalKeysToReEliminate(
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const BayesTree& bayesTree,
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@ -102,20 +82,21 @@ public:
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}
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checkedCliques.insert(clique);
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bool is_leaf = clique->children.empty();
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bool need_reeliminate = false;
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bool has_non_marginalizable_ahead = false;
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for (Key i: clique->conditional()->frontals()) {
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if (marginalizableKeySet.count(i)) {
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if (has_non_marginalizable_ahead) {
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// Case 2 in the docstring
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need_reeliminate = true;
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break;
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} else {
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// Check whether there're child nodes dependent on this key.
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// Check whether there's a child node dependent on this key.
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for(const sharedClique& child: clique->children) {
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if (std::find(child->conditional()->beginParents(),
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child->conditional()->endParents(), i)
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!= child->conditional()->endParents()) {
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// Case 1 in the docstring
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need_reeliminate = true;
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break;
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}
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@ -127,10 +108,11 @@ public:
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}
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if (!need_reeliminate) {
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// No variable needs to be reeliminated
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continue;
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} else {
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// need to re-eliminate this clique and all its children that depend on
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// a marginalizable key
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// Need to reeliminate the current clique and all its children
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// that rely on a marginalizable key.
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for (Key i: clique->conditional()->frontals()) {
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additionalKeys.insert(i);
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for (const sharedClique& child: clique->children) {
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