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// Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package ai.vespa.models.evaluation;
import com.google.common.annotations.Beta;
import com.yahoo.searchlib.rankingexpression.ExpressionFunction;
import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
import com.yahoo.tensor.Tensor;
import com.yahoo.tensor.TensorType;
/**
* An evaluator which can be used to evaluate a single function once.
*
* @author bratseth
*/
@Beta
// This wraps all access to the context and the ranking expression to avoid incorrect usage
public class FunctionEvaluator {
private final ExpressionFunction function;
private final LazyArrayContext context;
private boolean evaluated = false;
FunctionEvaluator(ExpressionFunction function, LazyArrayContext context) {
this.function = function;
this.context = context;
}
/**
* Binds the given variable referred in this expression to the given value.
*
* @param name the variable to bind
* @param value the value this becomes bound to
* @return this for chaining
*/
public FunctionEvaluator bind(String name, Tensor value) {
if (evaluated)
throw new IllegalStateException("You cannot bind a value in a used evaluator");
context.put(name, new TensorValue(value));
return this;
}
/**
* Binds the given variable referred in this expression to the given value.
* This is equivalent to <code>bind(name, Tensor.Builder.of(TensorType.empty).cell(value).build())</code>
*
* @param name the variable to bind
* @param value the value this becomes bound to
* @return this for chaining
*/
public FunctionEvaluator bind(String name, double value) {
return bind(name, Tensor.Builder.of(TensorType.empty).cell(value).build());
}
public Tensor evaluate() {
evaluated = true;
return function.getBody().evaluate(context).asTensor();
}
public LazyArrayContext context() { return context; }
}
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