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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.tensor.functions;
import com.yahoo.tensor.evaluation.EvaluationContext;
import com.yahoo.tensor.evaluation.MapEvaluationContext;
import com.yahoo.tensor.evaluation.Name;
import com.yahoo.tensor.evaluation.TypeContext;
import com.yahoo.tensor.Tensor;
import com.yahoo.tensor.TensorType;
import com.yahoo.tensor.TensorType.Dimension;
import java.util.List;
import java.util.Objects;
import java.util.Optional;
/**
* Convenience for cosine similarity between vectors.
* cosine_similarity(a, b, mydim) == sum(a*b, mydim) / sqrt(sum(a*a, mydim) * sum(b*b, mydim)).
*
* @author arnej
*/
public class CosineSimilarity extends TensorFunction {
private final TensorFunction arg1;
private final TensorFunction arg2;
private final String dimension;
public CosineSimilarity(TensorFunction argument1,
TensorFunction argument2,
String dimension)
{
this.arg1 = argument1;
this.arg2 = argument2;
this.dimension = dimension;
}
@Override
public List> arguments() { return List.of(arg1, arg2); }
@Override
public TensorFunction withArguments(List> arguments) {
if ( arguments.size() != 2)
throw new IllegalArgumentException("CosineSimilarity must have 2 arguments, got " + arguments.size());
return new CosineSimilarity<>(arguments.get(0), arguments.get(1), dimension);
}
@Override
public TensorType type(TypeContext context) {
TensorType t1 = arg1.toPrimitive().type(context);
TensorType t2 = arg2.toPrimitive().type(context);
var resolvedDimension = context.resolveBinding(dimension);
var d1 = t1.dimension(resolvedDimension);
var d2 = t2.dimension(resolvedDimension);
if (d1.isEmpty() || d2.isEmpty()
|| d1.get().type() != Dimension.Type.indexedBound
|| d2.get().type() != Dimension.Type.indexedBound
|| ! d1.get().size().equals(d2.get().size()))
{
throw new IllegalArgumentException("cosine_similarity expects both arguments to have the '"
+ resolvedDimension + "' dimension with same size, but input types were "
+ t1 + " and " + t2);
}
return toPrimitive().type(context);
}
/** Evaluates this by first converting it to a primitive function */
@Override
public Tensor evaluate(EvaluationContext context) {
return toPrimitive().evaluate(context);
}
@Override
public PrimitiveTensorFunction toPrimitive() {
TensorFunction a = arg1.toPrimitive();
TensorFunction b = arg2.toPrimitive();
var aa = new Join<>(a, a, ScalarFunctions.multiply());
var ab = new Join<>(a, b, ScalarFunctions.multiply());
var bb = new Join<>(b, b, ScalarFunctions.multiply());
var dot_aa = new Reduce<>(aa, Reduce.Aggregator.sum, dimension);
var dot_ab = new Reduce<>(ab, Reduce.Aggregator.sum, dimension);
var dot_bb = new Reduce<>(bb, Reduce.Aggregator.sum, dimension);
var aabb = new Join<>(dot_aa, dot_bb, ScalarFunctions.multiply());
var sqrt_aabb = new Map<>(aabb, ScalarFunctions.sqrt());
return new Join<>(dot_ab, sqrt_aabb, ScalarFunctions.divide());
}
@Override
public String toString(ToStringContext context) {
return "cosine_similarity(" + arg1.toString(context) + ", " + arg2.toString(context) + ", " + context.resolveBinding(dimension) + ")";
}
@Override
public int hashCode() { return Objects.hash("cosine_similarity", arg1, arg2, dimension); }
}