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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.rankingexpression.evaluation.tensoroptimization;
import com.yahoo.searchlib.rankingexpression.RankingExpression;
import com.yahoo.searchlib.rankingexpression.Reference;
import com.yahoo.searchlib.rankingexpression.evaluation.ContextIndex;
import com.yahoo.searchlib.rankingexpression.evaluation.OptimizationReport;
import com.yahoo.searchlib.rankingexpression.evaluation.Optimizer;
import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
import com.yahoo.searchlib.rankingexpression.rule.TensorFunctionNode;
import com.yahoo.tensor.functions.Join;
import com.yahoo.tensor.functions.Reduce;
import com.yahoo.tensor.functions.ReduceJoin;
import com.yahoo.tensor.functions.TensorFunction;
import java.util.ArrayList;
import java.util.List;
/**
* Recognizes and optimizes tensor expressions.
*
* @author lesters
*/
public class TensorOptimizer extends Optimizer {
private OptimizationReport report;
@Override
public void optimize(RankingExpression expression, ContextIndex context, OptimizationReport report) {
if (!isEnabled()) return;
this.report = report;
expression.setRoot(optimize(expression.getRoot(), context));
report.note("Tensor expression optimization done");
}
private ExpressionNode optimize(ExpressionNode node, ContextIndex context) {
node = optimizeReduceJoin(node);
if (node instanceof CompositeNode) {
return optimizeChildren((CompositeNode)node, context);
}
return node;
}
private ExpressionNode optimizeChildren(CompositeNode node, ContextIndex context) {
List<ExpressionNode> children = node.children();
List<ExpressionNode> optimizedChildren = new ArrayList<>(children.size());
for (ExpressionNode child : children)
optimizedChildren.add(optimize(child, context));
return node.setChildren(optimizedChildren);
}
/**
* Recognized a reduce followed by a join. In many cases, chunking these
* two operations together is significantly more efficient than evaluating
* each on its own, avoiding the cost of a temporary tensor.
*
* Note that this does not guarantee that the optimization is performed.
* The ReduceJoin class determines whether or not the arguments are
* compatible with the optimization.
*/
private ExpressionNode optimizeReduceJoin(ExpressionNode node) {
if ( ! (node instanceof TensorFunctionNode)) {
return node;
}
TensorFunction<Reference> function = ((TensorFunctionNode) node).function();
if ( ! (function instanceof Reduce)) {
return node;
}
List<ExpressionNode> children = ((TensorFunctionNode) node).children();
if (children.size() != 1) {
return node;
}
ExpressionNode child = children.get(0);
if ( ! (child instanceof TensorFunctionNode)) {
return node;
}
TensorFunction<Reference> argument = ((TensorFunctionNode) child).function();
if (argument instanceof Join) {
report.incMetric("Replaced reduce->join", 1);
return new TensorFunctionNode(new ReduceJoin<>((Reduce<Reference>)function, (Join<Reference>)argument));
}
return node;
}
}
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