TensorProductPairKernel.cpp

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/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2009 Soeren Sonnenburg
 * Copyright (C) 2009 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#include "lib/common.h"
#include "lib/Mathematics.h"
#include "kernel/TensorProductPairKernel.h"
#include "features/SimpleFeatures.h"
#include "lib/io.h"

using namespace shogun;

CTensorProductPairKernel::CTensorProductPairKernel(int32_t size, CKernel* s)
: CSimpleKernel<int32_t>(size), subkernel(s)
{
    SG_REF(subkernel);
}

CTensorProductPairKernel::CTensorProductPairKernel(CSimpleFeatures<int32_t>* l, CSimpleFeatures<int32_t>* r, CKernel* s)
: CSimpleKernel<int32_t>(10), subkernel(s)
{
    SG_REF(subkernel);
    init(l, r);
}

CTensorProductPairKernel::~CTensorProductPairKernel()
{
    SG_UNREF(subkernel);
    cleanup();
}

bool CTensorProductPairKernel::init(CFeatures* l, CFeatures* r)
{
    CSimpleKernel<int32_t>::init(l, r);
    init_normalizer();
    return true;
}

float64_t CTensorProductPairKernel::compute(int32_t idx_a, int32_t idx_b)
{
  int32_t alen, blen;
  bool afree, bfree;

  int32_t* avec=((CSimpleFeatures<int32_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
  int32_t* bvec=((CSimpleFeatures<int32_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);

  ASSERT(alen==2);
  ASSERT(blen==2);

  CKernel* k=subkernel;
  ASSERT(k && k->has_features());

  int32_t a=avec[0];
  int32_t b=avec[1];
  int32_t c=bvec[0];
  int32_t d=bvec[1];

  float64_t result = k->kernel(a,c)*k->kernel(b,d) + k->kernel(a,d)*k->kernel(b,c);

  ((CSimpleFeatures<int32_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
  ((CSimpleFeatures<int32_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);

  return result;
}