// Code extracted from ulmBLAS: https://github.com/michael-lehn/ulmBLAS-core

#ifndef GEMM_HPP
#define GEMM_HPP
#include <algorithm>

//-- Config --------------------------------------------------------------------
template <typename T>
struct BlockSize
{
    static const int MC = 64;
    static const int KC = 64;
    static const int NC = 256;
    static const int MR = 8;
    static const int NR = 8;
    static_assert(MC>0 && KC>0 && NC>0 && MR>0 && NR>0, "Invalid block size.");
    static_assert(MC % MR == 0, "MC must be a multiple of MR.");
    static_assert(NC % NR == 0, "NC must be a multiple of NR.");
};


template <>
struct BlockSize<double>
{
    static const int MC = 256;
    static const int KC = 256;
    static const int NC = 4096;
    static const int MR = 4;
    static const int NR = 8;
    static_assert(MC>0 && KC>0 && NC>0 && MR>0 && NR>0, "Invalid block size.");
    static_assert(MC % MR == 0, "MC must be a multiple of MR.");
    static_assert(NC % NR == 0, "NC must be a multiple of NR.");
};

//-- aux routines --------------------------------------------------------------
template <typename Index, typename Alpha, typename TX, typename TY>
void
geaxpy(Index m, Index n,
       const Alpha &alpha,
       const TX *X, Index incRowX, Index incColX,
       TY       *Y, Index incRowY, Index incColY)
{
    for (Index j=0; j<n; ++j) {
        for (Index i=0; i<m; ++i) {
            Y[i*incRowY+j*incColY] += alpha*X[i*incRowX+j*incColX];
        }
    }
}

template <typename Index, typename Alpha, typename TX>
void
gescal(Index m, Index n,
       const Alpha &alpha,
       TX *X, Index incRowX, Index incColX)
{
    for (Index j=0; j<n; ++j) {
        for (Index i=0; i<m; ++i) {
            X[i*incRowX+j*incColX] *= alpha;
        }
    }
}

//-- Micro Kernel --------------------------------------------------------------
template <typename Index, typename T>
void
ugemm(Index kc, T alpha,
      const T *A, const T *B,
      T beta,
      T *C, Index incRowC, Index incColC)
{
    const Index MR = BlockSize<T>::MR;
    const Index NR = BlockSize<T>::NR;
    T P[BlockSize<T>::MR*BlockSize<T>::NR];

    for (Index l=0; l<MR*NR; ++l) {
        P[l] = 0;
    }
    for (Index l=0; l<kc; ++l) {
        for (Index j=0; j<NR; ++j) {
            for (Index i=0; i<MR; ++i) {
                P[i+j*MR] += A[i+l*MR]*B[l*NR+j];
            }
        }
    }
    for (Index j=0; j<NR; ++j) {
        for (Index i=0; i<MR; ++i) {
            C[i*incRowC+j*incColC] *= beta;
            C[i*incRowC+j*incColC] += alpha*P[i+j*MR];
        }
    }
}


//-- Macro Kernel --------------------------------------------------------------
template <typename Index, typename T, typename Beta, typename TC>
void
mgemm(Index mc, Index nc, Index kc,
      T alpha,
      const T *A, const T *B,
      Beta beta,
      TC *C, Index incRowC, Index incColC)
{
    const Index MR = BlockSize<T>::MR;
    const Index NR = BlockSize<T>::NR;
    T C_[BlockSize<T>::MR*BlockSize<T>::NR];
    const Index mp  = (mc+MR-1) / MR;
    const Index np  = (nc+NR-1) / NR;
    const Index mr_ = mc % MR;
    const Index nr_ = nc % NR;

    for (Index j=0; j<np; ++j) {
        const Index nr = (j!=np-1 || nr_==0) ? NR : nr_;

        for (Index i=0; i<mp; ++i) {
            const Index mr = (i!=mp-1 || mr_==0) ? MR : mr_;

            if (mr==MR && nr==NR) {
                ugemm(kc, alpha,
                      &A[i*kc*MR], &B[j*kc*NR],
                      beta,
                      &C[i*MR*incRowC+j*NR*incColC],
                      incRowC, incColC);
            } else {
                std::fill_n(C_, MR*NR, T(0));
                ugemm(kc, alpha,
                      &A[i*kc*MR], &B[j*kc*NR],
                      T(0),
                      C_, Index(1), MR);
                gescal(mr, nr, beta,
                       &C[i*MR*incRowC+j*NR*incColC],
                       incRowC, incColC);
                geaxpy(mr, nr, T(1), C_, Index(1), MR,
                       &C[i*MR*incRowC+j*NR*incColC],
                       incRowC, incColC);
            }
        }
    }
}

//-- Packing blocks ------------------------------------------------------------
template <typename Index, typename TA, typename T>
void
pack_A(Index mc, Index kc,
       const TA *A, Index incRowA, Index incColA,
       T *p)
{
    Index MR = BlockSize<T>::MR;
    Index mp = (mc+MR-1) / MR;

    for (Index j=0; j<kc; ++j) {
        for (Index l=0; l<mp; ++l) {
            for (Index i0=0; i0<MR; ++i0) {
                Index i  = l*MR + i0;
                Index nu = l*MR*kc + j*MR + i0;
                p[nu]   = (i<mc) ? A[i*incRowA+j*incColA]
                                 : T(0);
            }
        }
    }
}

template <typename Index, typename TB, typename T>
void
pack_B(Index kc, Index nc,
       const TB *B, Index incRowB, Index incColB,
       T *p)
{
    Index NR = BlockSize<T>::NR;
    Index np = (nc+NR-1) / NR;

    for (Index l=0; l<np; ++l) {
        for (Index j0=0; j0<NR; ++j0) {
            for (Index i=0; i<kc; ++i) {
                Index j  = l*NR+j0;
                Index nu = l*NR*kc + i*NR + j0;
                p[nu]   = (j<nc) ? B[i*incRowB+j*incColB]
                                 : T(0);
            }
        }
    }
}

//-- Frame routine -------------------------------------------------------------
template <typename Index, typename Alpha,
         typename TA, typename TB,
         typename Beta,
         typename TC>
void
gemm(Index m, Index n, Index k,
     Alpha alpha,
     const TA *A, Index incRowA, Index incColA,
     const TB *B, Index incRowB, Index incColB,
     Beta beta,
     TC *C, Index incRowC, Index incColC)
{
    typedef typename std::common_type<Alpha, TA, TB>::type  T;

    const Index MC = BlockSize<T>::MC;
    const Index NC = BlockSize<T>::NC;
    const Index KC = BlockSize<T>::KC;
    const Index mb = (m+MC-1) / MC;
    const Index nb = (n+NC-1) / NC;
    const Index kb = (k+KC-1) / KC;
    const Index mc_ = m % MC;
    const Index nc_ = n % NC;
    const Index kc_ = k % KC;

    T *A_ = new T[MC*KC];
    T *B_ = new T[KC*NC];

    if (alpha==Alpha(0) || k==0) {
        gescal(m, n, beta, C, incRowC, incColC);
        return;
    }

    for (Index j=0; j<nb; ++j) {
        Index nc = (j!=nb-1 || nc_==0) ? NC : nc_;

        for (Index l=0; l<kb; ++l) {
            Index   kc  = (l!=kb-1 || kc_==0) ? KC : kc_;
            Beta beta_  = (l==0) ? beta : Beta(1);

            pack_B(kc, nc,
                   &B[l*KC*incRowB+j*NC*incColB],
                   incRowB, incColB,
                   B_);

            for (Index i=0; i<mb; ++i) {
                Index mc = (i!=mb-1 || mc_==0) ? MC : mc_;

                pack_A(mc, kc,
                       &A[i*MC*incRowA+l*KC*incColA],
                       incRowA, incColA,
                       A_);

                mgemm(mc, nc, kc,
                      T(alpha), A_, B_, beta_,
                      &C[i*MC*incRowC+j*NC*incColC],
                      incRowC, incColC);
            }
        }
    }
    free(A_);
    free(B_);
}

#endif