Max.h

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/*
 * Copyright (c) The Shogun Machine Learning Toolbox
 * Written (w) 2014 Khaled Nasr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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 */

#ifndef MAX_IMPL_H_
#define MAX_IMPL_H_

#include <shogun/lib/config.h>
#include <shogun/lib/SGMatrix.h>
#include <shogun/lib/SGVector.h>
#include <shogun/mathematics/Math.h>

#ifdef HAVE_EIGEN3
#include <shogun/mathematics/eigen3.h>
#endif // HAVE_EIGEN3

#ifdef HAVE_VIENNACL
#include <shogun/mathematics/linalg/internal/opencl_util.h>
#include <shogun/lib/GPUMatrix.h>
#include <shogun/lib/GPUVector.h>
#endif

#include <string>

namespace shogun
{

namespace linalg
{

namespace implementation
{

template <enum Backend,class Matrix>
struct max
{
    typedef typename Matrix::Scalar T;

    static T compute(Matrix m);
};

template <class Matrix>
struct max<Backend::NATIVE, Matrix>
{
    typedef typename Matrix::Scalar T;

    static T compute(SGMatrix<T> mat)
    {
        REQUIRE(mat.num_cols*mat.num_rows > 0, "Matrix can not be empty!\n");
        return compute(mat.matrix, mat.num_cols*mat.num_rows);
    }

    static T compute(SGVector<T> vec)
    {
        REQUIRE(vec.vlen > 0, "Vector can not be empty!\n");
        return compute(vec.vector, vec.vlen);
    }

    static T compute(T* vec, index_t len)
    {
        return *std::max_element(vec, vec+len);
    }
};

#ifdef HAVE_EIGEN3

template <class Matrix>
struct max<Backend::EIGEN3,Matrix>
{
    typedef typename Matrix::Scalar T;

    typedef Eigen::Matrix<T,Eigen::Dynamic,Eigen::Dynamic> MatrixXt;

    typedef Eigen::Matrix<T,Eigen::Dynamic,1> VectorXt;

    static T compute(SGMatrix<T> mat)
    {
        Eigen::Map<MatrixXt> m = mat;

        return m.maxCoeff();
    }

    static T compute(SGVector<T> vec)
    {
        Eigen::Map<VectorXt> v = vec;

        return v.maxCoeff();
    }
};
#endif // HAVE_EIGEN3

#ifdef HAVE_VIENNACL

template <class Matrix>
struct max<Backend::VIENNACL,Matrix>
{
    typedef typename Matrix::Scalar T;

    template <class T>
    static viennacl::ocl::kernel& generate_kernel()
    {
        std::string kernel_name = "max_" + ocl::get_type_string<T>();

        if (ocl::kernel_exists(kernel_name))
            return ocl::get_kernel(kernel_name);

        std::string source = ocl::generate_kernel_preamble<T>(kernel_name);

        source.append(
            R"(
                __kernel void KERNEL_NAME(
                    __global DATATYPE* vec, int size, int offset,
                    __global DATATYPE* result)
                {
                    __local DATATYPE buffer[WORK_GROUP_SIZE_1D];

                    int local_id = get_local_id(0);

                    DATATYPE thread_max = -INFINITY;
                    for (int i=local_id; i<size; i+=WORK_GROUP_SIZE_1D)
                    {
                        DATATYPE v = vec[i+offset];
                        thread_max = max(v, thread_max);
                    }

                    buffer[local_id] = thread_max;

                    for (int j = WORK_GROUP_SIZE_1D/2; j > 0; j = j>>1)
                    {
                        barrier(CLK_LOCAL_MEM_FENCE);
                        if (local_id < j)
                            buffer[local_id] = max(buffer[local_id], buffer[local_id + j]);
                    }

                    barrier(CLK_LOCAL_MEM_FENCE);

                    if (get_global_id(0)==0)
                        *result = buffer[0];
                }
            )"
        );

        viennacl::ocl::kernel& kernel = ocl::compile_kernel(kernel_name, source);

        kernel.local_work_size(0, OCL_WORK_GROUP_SIZE_1D);
        kernel.global_work_size(0, OCL_WORK_GROUP_SIZE_1D);

        return kernel;
    }

    static T compute(CGPUMatrix<T> mat)
    {
        viennacl::ocl::kernel& kernel = generate_kernel<T>();

        CGPUVector<T> result(1);

        viennacl::ocl::enqueue(kernel(mat.vcl_matrix(),
            cl_int(mat.num_rows*mat.num_cols), cl_int(mat.offset),
            result.vcl_vector()));

        return result[0];
    }

    static T compute(CGPUVector<T> vec)
    {
        viennacl::ocl::kernel& kernel = generate_kernel<T>();

        CGPUVector<T> result(1);

        viennacl::ocl::enqueue(kernel(vec.vcl_vector(),
            cl_int(vec.vlen), cl_int(vec.offset),
            result.vcl_vector()));

        return result[0];
    }
};
#endif // HAVE_VIENNACL

}

}

}
#endif // MAX_IMPL_H_