#include "ggml-blas.h"
#include "ggml-backend-impl.h"

#include <future>
#include <vector>

#if defined(GGML_USE_ACCELERATE)
#   include <Accelerate/Accelerate.h>
#elif defined(GGML_BLAS_USE_MKL)
#   include <mkl.h>
#else
#   include <cblas.h>
#   ifdef BLIS_ENABLE_CBLAS
#       include <blis.h>
#   endif
#endif

struct ggml_backend_blas_context {
    int n_threads = GGML_DEFAULT_N_THREADS;
    std::unique_ptr<char[]> work_data;
    size_t work_size = 0;
#ifndef GGML_USE_OPENMP
    std::vector<std::future<void>> tasks;
#endif
};

// helper function to determine if it is better to use BLAS or not
// for large matrices, BLAS is faster
static bool ggml_backend_blas_use_blas(const struct ggml_tensor * dst) {
    const struct ggml_tensor * src0 = dst->src[0];
    const struct ggml_tensor * src1 = dst->src[1];

    const int64_t ne10 = src1->ne[0];

    const int64_t ne0 = dst->ne[0];
    const int64_t ne1 = dst->ne[1];

    // TODO: find the optimal values for these
    if (ggml_is_contiguous(src0) &&
        ggml_is_contiguous(src1) &&
        src1->type == GGML_TYPE_F32 &&
        (ne0 >= 32 && ne1 >= 32 && ne10 >= 32)) {

        /*printf("BLAS: %d %d %d %d %d\n", ne0, ne1, ne10, ne00, ne01);*/
        return true;
    }

    return false;
}

static void ggml_backend_blas_mul_mat(ggml_backend_blas_context * ctx, struct ggml_tensor * dst) {
    const struct ggml_tensor * src0 = dst->src[0];
    const struct ggml_tensor * src1 = dst->src[1];

    GGML_TENSOR_BINARY_OP_LOCALS

    const enum ggml_type type = src0->type;

    GGML_ASSERT(ne0 == ne01);
    GGML_ASSERT(ne1 == ne11);
    GGML_ASSERT(ne2 == ne12);
    GGML_ASSERT(ne3 == ne13);

    // we don't support permuted src0 or src1
    GGML_ASSERT(nb00 == ggml_type_size(type));
    GGML_ASSERT(nb10 == ggml_type_size(src1->type));

    // dst cannot be transposed or permuted
    GGML_ASSERT(nb0 == sizeof(float));
    GGML_ASSERT(nb0 <= nb1);
    GGML_ASSERT(nb1 <= nb2);
    GGML_ASSERT(nb2 <= nb3);

    // broadcast factors
    const int64_t r2 = ne12/ne02;
    const int64_t r3 = ne13/ne03;

    const int64_t ne_plane      = ne01*ne00;
    const size_t  desired_wsize = type == GGML_TYPE_F32 ? 0 : ne03*ne02*ne_plane*sizeof(float);

    if (ctx->work_size < desired_wsize) {
        ctx->work_data.reset(new char[desired_wsize]);
        ctx->work_size = desired_wsize;
    }
    void * wdata = ctx->work_data.get();

    // convert src0 to float
    if (type != GGML_TYPE_F32) {
        ggml_type_traits_t type_traits = ggml_internal_get_type_traits(type);
        ggml_to_float_t const to_float = type_traits.to_float;

        for (int64_t i03 = 0; i03 < ne03; i03++) {
            for (int64_t i02 = 0; i02 < ne02; i02++) {
                const void  *       x      = (char *)  src0->data + i02*nb02          + i03*nb03;
                      float * const wplane = (float *) wdata      + i02*ne_plane      + i03*ne02*ne_plane;

                const int min_cols_per_thread = 4096;
                const int min_rows_per_thread = std::max((int)(min_cols_per_thread/ne00), 1);
                const int n_threads = std::max(std::min(ctx->n_threads, (int)(ne01/min_rows_per_thread)), 1);

#ifdef GGML_USE_OPENMP
                #pragma omp parallel for num_threads(n_threads)
                for (int64_t i01 = 0; i01 < ne01; i01++) {
                    to_float((const char *) x + i01*nb01, wplane + i01*ne00, ne00);
                }
#else
                for (int i = 1; i < n_threads; i++) {
                    const int64_t start =       i*ne01/n_threads;
                    const int64_t end   = (i + 1)*ne01/n_threads;
                    if (start < end) {
                        ctx->tasks.push_back(std::async(std::launch::async, [=]() {
                            for (int64_t i01 = start; i01 < end; i01++) {
                                to_float((const char *) x + i01*nb01, wplane + i01*ne00, ne00);
                            }
                        }));
                    }
                }
                {
                    // reuse the current thread for the first task
                    const int64_t start = 0;
                    const int64_t end   = ne01/n_threads;
                    for (int64_t i01 = start; i01 < end; i01++) {
                        to_float((const char *) x + i01*nb01, wplane + i01*ne00, ne00);
                    }
                }
#endif
            }
        }

#ifndef GGML_USE_OPENMP
        // wait for all tasks to finish
        for (auto & task : ctx->tasks) {
            task.get();
        }
        ctx->tasks.clear();
#endif
    }

#if defined(OPENBLAS_VERSION)
    openblas_set_num_threads(ctx->n_threads);
#endif

#if defined(BLIS_ENABLE_CBLAS)
    bli_thread_set_num_threads(ctx->n_threads);
#endif

    for (int64_t i13 = 0; i13 < ne13; i13++) {
        for (int64_t i12 = 0; i12 < ne12; i12++) {
            const int64_t i03 = i13/r3;
            const int64_t i02 = i12/r2;

            const float * x = (float *) ((char *) src0->data + i02*nb02 + i03*nb03);
            const float * y = (float *) ((char *) src1->data + i12*nb12 + i13*nb13);
                  float * d = (float *) ((char *)  dst->data + i12*nb2  + i13*nb3);

            if (type != GGML_TYPE_F32) {
                x = (float *) wdata + i02*ne_plane + i03*ne02*ne_plane;
            }

            cblas_sgemm(CblasRowMajor, CblasNoTrans, CblasTrans,
                        ne1, ne01, ne10,
                        1.0f,   y, ne10,
                                x, ne00,
                        0.0f,   d, ne01);
        }
    }
}

static void ggml_backend_blas_out_prod(ggml_backend_blas_context * ctx, struct ggml_tensor * dst) {
    const struct ggml_tensor * src0 = dst->src[0];
    const struct ggml_tensor * src1 = dst->src[1];

    GGML_TENSOR_BINARY_OP_LOCALS

    GGML_ASSERT(ne0  == ne00);
    GGML_ASSERT(ne1  == ne10);
    GGML_ASSERT(ne2  == ne02);
    GGML_ASSERT(ne02 == ne12);
    GGML_ASSERT(ne3  == ne13);
    GGML_ASSERT(ne03 == ne13);

    // we don't support permuted src0 or src1
    GGML_ASSERT(nb00 == sizeof(float));

    // dst cannot be transposed or permuted
    GGML_ASSERT(nb0 == sizeof(float));
    // GGML_ASSERT(nb0 <= nb1);
    // GGML_ASSERT(nb1 <= nb2);
    // GGML_ASSERT(nb2 <= nb3);

    // Arguments to ggml_compute_forward_out_prod (expressed as major,minor)
    // src0: (k,n)
    // src1: (k,m)
    // dst:  (m,n)
    //
    // Arguments to sgemm (see https://github.com/Reference-LAPACK/lapack/blob/master/BLAS/SRC/sgemm.f)
    // Also expressed as (major,minor)
    // a: (m,k): so src1 transposed
    // b: (k,n): so src0
    // c: (m,n)
    //
    // However, if ggml_is_transposed(src1) is true, then
    // src1->data already contains a transposed version, so sgemm mustn't
    // transpose it further.

    int n = src0->ne[0];
    int k = src0->ne[1];
    int m = src1->ne[0];

    CBLAS_TRANSPOSE transposeA;
    int lda;

    if (!ggml_is_transposed(src1)) {
        transposeA = CblasTrans;
        lda = m;
    } else {
        transposeA = CblasNoTrans;
        lda = k;
    }

    float * a = (float *) ((char *) src1->data);
    float * b = (float *) ((char *) src0->data);
    float * c = (float *) ((char *) dst->data);

    cblas_sgemm(CblasRowMajor, transposeA, CblasNoTrans, m, n, k, 1.0, a, lda, b, n, 0.0, c, n);

    GGML_UNUSED(ctx);
}

// backend interface

GGML_CALL static const char * ggml_backend_blas_name(ggml_backend_t backend) {
    return "BLAS";

    GGML_UNUSED(backend);
}

GGML_CALL static void ggml_backend_blas_free(ggml_backend_t backend) {
    ggml_backend_blas_context * ctx = (ggml_backend_blas_context *)backend->context;
    delete ctx;
    delete backend;
}

GGML_CALL static ggml_backend_buffer_type_t ggml_backend_blas_get_default_buffer_type(ggml_backend_t backend) {
    return ggml_backend_cpu_buffer_type();

    GGML_UNUSED(backend);
}

GGML_CALL static enum ggml_status ggml_backend_blas_graph_compute(ggml_backend_t backend, struct ggml_cgraph * cgraph) {
    ggml_backend_blas_context * ctx = (ggml_backend_blas_context *)backend->context;

    for (int i = 0; i < cgraph->n_nodes; i++) {
        struct ggml_tensor * node = cgraph->nodes[i];

        switch (node->op) {
            case GGML_OP_MUL_MAT:
                ggml_backend_blas_mul_mat(ctx, node);
                break;

            case GGML_OP_OUT_PROD:
                ggml_backend_blas_out_prod(ctx, node);
                break;

            case GGML_OP_NONE:
            case GGML_OP_RESHAPE:
            case GGML_OP_VIEW:
            case GGML_OP_PERMUTE:
            case GGML_OP_TRANSPOSE:
                break;

            default:
                fprintf(stderr, "%s: unsupported op %s\n", __func__, ggml_op_desc(node));
                GGML_ASSERT(false);
        }
    }

    return GGML_STATUS_SUCCESS;

    GGML_UNUSED(backend);
}

GGML_CALL static bool ggml_backend_blas_supports_op(ggml_backend_t backend, const struct ggml_tensor * op) {
    const struct ggml_tensor * src0 = op->src[0];
    const struct ggml_tensor * src1 = op->src[1];

    return (op->op == GGML_OP_MUL_MAT  && ggml_backend_blas_use_blas(op)) ||
           (op->op == GGML_OP_OUT_PROD && op->src[0]->type == GGML_TYPE_F32 &&
                                          op->src[1]->type == GGML_TYPE_F32 &&
                                          ggml_is_matrix(src0) &&
                                          ggml_is_matrix(src1) &&
                                          ggml_is_contiguous(src0) &&
                                          (ggml_is_contiguous(src1) || ggml_is_transposed(src1)));

    GGML_UNUSED(backend);
}

GGML_CALL static bool ggml_backend_blas_supports_buft(ggml_backend_t backend, ggml_backend_buffer_type_t buft) {
    return ggml_backend_buft_is_host(buft);

    GGML_UNUSED(backend);
}

static struct ggml_backend_i blas_backend_i = {
    /* .get_name                = */ ggml_backend_blas_name,
    /* .free                    = */ ggml_backend_blas_free,
    /* .get_default_buffer_type = */ ggml_backend_blas_get_default_buffer_type,
    /* .set_tensor_async        = */ NULL,
    /* .get_tensor_async        = */ NULL,
    /* .cpy_tensor_async        = */ NULL,
    /* .synchronize             = */ NULL,
    /* .graph_plan_create       = */ NULL,
    /* .graph_plan_free         = */ NULL,
    /* .graph_plan_update       = */ NULL,
    /* .graph_plan_compute      = */ NULL,
    /* .graph_compute           = */ ggml_backend_blas_graph_compute,
    /* .supports_op             = */ ggml_backend_blas_supports_op,
    /* .supports_buft           = */ ggml_backend_blas_supports_buft,
    /* .offload_op              = */ NULL,
    /* .event_new               = */ NULL,
    /* .event_free              = */ NULL,
    /* .event_record            = */ NULL,
    /* .event_wait              = */ NULL,
    /* .event_synchronize       = */ NULL,
};

static ggml_guid_t ggml_backend_blas_guid(void) {
    static ggml_guid guid = { 0x12, 0xa8, 0xae, 0xf4, 0xc0, 0x1e, 0x61, 0x97, 0x8f, 0xeb, 0x33, 0x04, 0xa1, 0x33, 0x51, 0x2d };
    return &guid;
}

ggml_backend_t ggml_backend_blas_init(void) {
    ggml_backend_blas_context * ctx = new ggml_backend_blas_context;

    ggml_backend_t backend = new ggml_backend {
        /* .guid      = */ ggml_backend_blas_guid(),
        /* .interface = */ blas_backend_i,
        /* .context   = */ ctx,
    };

#if !defined(NDEBUG) && defined(OPENBLAS_VERSION) && defined(GGML_USE_OPENMP)
    if (openblas_get_parallel() != OPENBLAS_OPENMP) {
        fprintf(stderr, "%s: warning: ggml is using OpenMP, but OpenBLAS was compiled without OpenMP support\n", __func__);
    }
#endif

#if !defined(NDEBUG) && defined(BLIS_ENABLE_CBLAS) && defined(GGML_USE_OPENMP) && !defined(BLIS_ENABLE_OPENMP)
    fprintf(stderr, "%s: warning: ggml is using OpenMP, but BLIS was compiled without OpenMP support\n", __func__);
#endif

    return backend;
}

GGML_CALL bool ggml_backend_is_blas(ggml_backend_t backend) {
    return backend != NULL && ggml_guid_matches(backend->guid, ggml_backend_blas_guid());
}

void ggml_backend_blas_set_n_threads(ggml_backend_t backend_blas, int n_threads) {
    GGML_ASSERT(ggml_backend_is_blas(backend_blas));

    ggml_backend_blas_context * ctx = (ggml_backend_blas_context *)backend_blas->context;
    ctx->n_threads = n_threads;
}