mpv.hpp

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/*
 *   Copyright 2021 Huawei Technologies Co., Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef _H_GRB_ALGORITHMS_MPV
#define _H_GRB_ALGORITHMS_MPV

#include <graphblas.hpp>


namespace grb {

    namespace algorithms {

        template< Descriptor descr, class Ring, typename IOType, typename InputType >
        RC mpv(
            Vector< IOType > &u,
            const Matrix< InputType > &A, const size_t k,
            const Vector< IOType > &v,
            Vector< IOType > &temp,
            const Ring &ring
        ) {
            static_assert( !(descr & descriptors::no_casting) ||
                    (std::is_same< IOType, typename Ring::D4 >::value &&
                        std::is_same< InputType, typename Ring::D2 >::value &&
                        std::is_same< IOType, typename Ring::D1 >::value &&
                        std::is_same< IOType, typename Ring::D3 >::value
                    ),
                "grb::mpv : some containers were passed with element types that do not"
                "match the given semiring domains."
            );

            // runtime check
            const size_t n = nrows( A );
            if( n != ncols( A ) ) {
                return ILLEGAL;
            }
            if( size( u ) != n || n != size( v ) ) {
                return MISMATCH;
            }
            if( size( temp ) != n ) {
                return MISMATCH;
            }
            if( capacity( u ) != n ) {
                return ILLEGAL;
            }
            if( capacity( temp ) != n ) {
                return ILLEGAL;
            }
            // catch trivial case
            if( k == 0 ) {
                return set< descr >( u, v );
            }
            // otherwise, do at least one multiplication
#ifdef _DEBUG
            std::cout << "init: input vector nonzeroes is " << grb::nnz( v ) << ".\n";
#endif
            RC ret = mxv< descr >( u, A, v, ring );
            if( k == 1 ) {
                return ret;
            }
            // do any remaining multiplications using a temporary output vector
            bool copy;
            ret = ret ? ret : clear( temp );
            for( size_t iterate = 1; ret == SUCCESS && iterate < k; iterate += 2 ) {
                // multiply with output into temporary
                copy = true;
#ifdef _DEBUG
                std::cout << "up: input vector nonzeroes is " << grb::nnz( u ) << "\n";
#endif
                ret = mxv< descr >( temp, A, u, ring );
                // check if this was the final multiplication
                assert( iterate <= k );
                if( iterate + 1 == k || ret != SUCCESS ) {
                    break;
                }
                // multiply with output into u
                copy = false;
#ifdef _DEBUG
                std::cout << "down: input vector nonzeroes is " << grb::nnz( temp ) << "\n";
#endif
                ret = mxv< descr >( u, A, temp, ring );
            }

            // swap u and temp, if required
            if( ret == SUCCESS && copy ) {
                std::swap( u, temp );
            }

            // done
            return ret;
        }

    } // namespace algorithms

} // namespace grb

#endif // end ``_H_GRB_ALGORITHMS_MPV''