/*
 * Copyright 2018 Anton Khirnov <anton@khirnov.net>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include <float.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <threadpool.h>

#include "common.h"
#include "cpu.h"
#include "ell_relax.h"
#include "log.h"
#include "mg2d_boundary.h"
#include "mg2d_boundary_internal.h"
#include "mg2d_constants.h"

static const double relax_factors[FD_STENCIL_MAX] = {
    [0] = 1.0 / 5,
    [1] = 1.0 / 7,
};

struct EllRelaxInternal {
    ptrdiff_t stride;
    double *u_base;
    double *rhs_base;
    double *residual_base;
    double *diff_coeffs_base[MG2D_DIFF_COEFF_NB];

    double *residual_max;
    size_t  residual_max_size;

    void (*residual_calc_line)(size_t linesize, double *dst, double *dst_max,
                               ptrdiff_t stride, const double *u, const double *rhs,
                               const double * const diff_coeffs[MG2D_DIFF_COEFF_NB],
                               const double *fd_factors);
    size_t calc_blocksize;
    ptrdiff_t residual_calc_offset;
    size_t residual_calc_size[2];
    double fd_factors[MG2D_DIFF_COEFF_NB];
    double relax_factor;

    TPContext *tp_internal;
};

static const struct {
    unsigned int stride_idx;
    unsigned int is_upper;
} boundary_def[] = {
    [MG2D_BOUNDARY_0L] = {
        .stride_idx = 0,
        .is_upper   = 0
    },
    [MG2D_BOUNDARY_0U] = {
        .stride_idx = 0,
        .is_upper   = 1,
    },
    [MG2D_BOUNDARY_1L] = {
        .stride_idx = 1,
        .is_upper   = 0,
    },
    [MG2D_BOUNDARY_1U] = {
        .stride_idx = 1,
        .is_upper   = 1,
    },
};

static const double fd_denoms[][MG2D_DIFF_COEFF_NB] = {
    {
        [MG2D_DIFF_COEFF_00] = 1.0,
        [MG2D_DIFF_COEFF_10] = 2.0,
        [MG2D_DIFF_COEFF_01] = 2.0,
        [MG2D_DIFF_COEFF_20] = 1.0,
        [MG2D_DIFF_COEFF_02] = 1.0,
        [MG2D_DIFF_COEFF_11] = 4.0,
    },
    {
        [MG2D_DIFF_COEFF_00] = 1.0,
        [MG2D_DIFF_COEFF_10] = 12.0,
        [MG2D_DIFF_COEFF_01] = 12.0,
        [MG2D_DIFF_COEFF_20] = 12.0,
        [MG2D_DIFF_COEFF_02] = 12.0,
        [MG2D_DIFF_COEFF_11] = 144.0,
    },
};

#if HAVE_EXTERNAL_ASM
void mg2di_residual_calc_line_s1_fma3(size_t linesize, double *dst, double *dst_max,
                                      ptrdiff_t stride, const double *u, const double *rhs,
                                      const double * const diff_coeffs[MG2D_DIFF_COEFF_NB],
                                      const double *fd_factors);
void mg2di_residual_calc_line_s2_fma3(size_t linesize, double *dst, double *dst_max,
                                      ptrdiff_t stride, const double *u, const double *rhs,
                                      const double * const diff_coeffs[MG2D_DIFF_COEFF_NB],
                                      const double *fd_factors);
#endif

static void
derivatives_calc_s1(double *dst, const double *u, const double *fd_factors, ptrdiff_t stride)
{
    dst[MG2D_DIFF_COEFF_00] = u[0];
    dst[MG2D_DIFF_COEFF_10] = (u[1]      - u[-1])      * fd_factors[MG2D_DIFF_COEFF_10];
    dst[MG2D_DIFF_COEFF_01] = (u[stride] - u[-stride]) * fd_factors[MG2D_DIFF_COEFF_01];

    dst[MG2D_DIFF_COEFF_20] = (u[1]      - 2.0 * u[0] + u[-1])      * fd_factors[MG2D_DIFF_COEFF_20];
    dst[MG2D_DIFF_COEFF_02] = (u[stride] - 2.0 * u[0] + u[-stride]) * fd_factors[MG2D_DIFF_COEFF_02];

    dst[MG2D_DIFF_COEFF_11] = (u[1 + stride] - u[stride - 1] - u[-stride + 1] + u[-stride - 1]) * fd_factors[MG2D_DIFF_COEFF_11];
}

static void
derivatives_calc_s2(double *dst, const double *u, const double *fd_factors, ptrdiff_t stride)
{
    const double val    = u[0];

    const double valxp1 = u[ 1];
    const double valxp2 = u[ 2];
    const double valxm1 = u[-1];
    const double valxm2 = u[-2];
    const double valyp1 = u[ 1 * stride];
    const double valyp2 = u[ 2 * stride];
    const double valym1 = u[-1 * stride];
    const double valym2 = u[-2 * stride];

    const double valxp1yp1 = u[ 1 + 1 * stride];
    const double valxp1yp2 = u[ 1 + 2 * stride];
    const double valxp1ym1 = u[ 1 - 1 * stride];
    const double valxp1ym2 = u[ 1 - 2 * stride];

    const double valxp2yp1 = u[ 2 + 1 * stride];
    const double valxp2yp2 = u[ 2 + 2 * stride];
    const double valxp2ym1 = u[ 2 - 1 * stride];
    const double valxp2ym2 = u[ 2 - 2 * stride];

    const double valxm1yp1 = u[-1 + 1 * stride];
    const double valxm1yp2 = u[-1 + 2 * stride];
    const double valxm1ym1 = u[-1 - 1 * stride];
    const double valxm1ym2 = u[-1 - 2 * stride];

    const double valxm2yp1 = u[-2 + 1 * stride];
    const double valxm2yp2 = u[-2 + 2 * stride];
    const double valxm2ym1 = u[-2 - 1 * stride];
    const double valxm2ym2 = u[-2 - 2 * stride];

    dst[MG2D_DIFF_COEFF_00] = val;
    dst[MG2D_DIFF_COEFF_10] = (-1.0 * valxp2 + 8.0 * valxp1      - 8.0 * valxm1 + 1.0 * valxm2) * fd_factors[MG2D_DIFF_COEFF_10];
    dst[MG2D_DIFF_COEFF_01] = (-1.0 * valyp2 + 8.0 * valyp1      - 8.0 * valym1 + 1.0 * valym2) * fd_factors[MG2D_DIFF_COEFF_01];

    dst[MG2D_DIFF_COEFF_20] = (-1.0 * valxp2 + 16.0 * valxp1 - 30.0 * val + 16.0 * valxm1 - 1.0 * valxm2) * fd_factors[MG2D_DIFF_COEFF_20];
    dst[MG2D_DIFF_COEFF_02] = (-1.0 * valyp2 + 16.0 * valyp1 - 30.0 * val + 16.0 * valym1 - 1.0 * valym2) * fd_factors[MG2D_DIFF_COEFF_02];

    dst[MG2D_DIFF_COEFF_11] = ( 1.0 * valxp2yp2 -  8.0 * valxp2yp1 +  8.0 * valxp2ym1 - 1.0 * valxp2ym2
                               -8.0 * valxp1yp2 + 64.0 * valxp1yp1 - 64.0 * valxp1ym1 + 8.0 * valxp1ym2
                               +8.0 * valxm1yp2 - 64.0 * valxm1yp1 + 64.0 * valxm1ym1 - 8.0 * valxm1ym2
                               -1.0 * valxm2yp2 +  8.0 * valxm2yp1 -  8.0 * valxm2ym1 + 1.0 * valxm2ym2) * fd_factors[MG2D_DIFF_COEFF_11];
}

static void residual_calc_line_s1_c(size_t linesize, double *dst, double *dst_max,
                                    ptrdiff_t stride, const double *u, const double *rhs,
                                    const double * const diff_coeffs[MG2D_DIFF_COEFF_NB],
                                    const double *fd_factors)
{
    double res_max = 0.0, res_abs;
    for (size_t i = 0; i < linesize; i++) {
        double u_vals[MG2D_DIFF_COEFF_NB];
        double res;

        derivatives_calc_s1(u_vals, u + i, fd_factors, stride);

        res = -rhs[i];
        for (int j = 0; j < ARRAY_ELEMS(u_vals); j++)
            res += u_vals[j] * diff_coeffs[j][i];
        dst[i] = res;

        res_abs = fabs(res);
        res_max = MAX(res_max, res_abs);
    }

    *dst_max = MAX(*dst_max, res_max);
}

static void residual_calc_line_s2_c(size_t linesize, double *dst, double *dst_max,
                                    ptrdiff_t stride, const double *u, const double *rhs,
                                    const double * const diff_coeffs[MG2D_DIFF_COEFF_NB],
                                    const double *fd_factors)
{
    double res_max = 0.0, res_abs;
    for (size_t i = 0; i < linesize; i++) {
        double u_vals[MG2D_DIFF_COEFF_NB];
        double res;

        derivatives_calc_s2(u_vals, u + i, fd_factors, stride);

        res = -rhs[i];
        for (int j = 0; j < ARRAY_ELEMS(u_vals); j++)
            res += u_vals[j] * diff_coeffs[j][i];
        dst[i] = res;

        res_abs = fabs(res);
        res_max = MAX(res_max, res_abs);
    }

    *dst_max = MAX(*dst_max, res_max);
}

static void residual_calc_task(void *arg, unsigned int job_idx, unsigned int thread_idx)
{
    EllRelaxContext  *ctx = arg;
    EllRelaxInternal *priv = ctx->priv;
    const ptrdiff_t offset = priv->residual_calc_offset + job_idx * priv->stride;
    const double *diff_coeffs[MG2D_DIFF_COEFF_NB];

    for (int i = 0; i < ARRAY_ELEMS(diff_coeffs); i++)
        diff_coeffs[i] = ctx->diff_coeffs[i] + offset;

    priv->residual_calc_line(priv->residual_calc_size[0], ctx->residual + offset,
                             priv->residual_max + thread_idx * priv->calc_blocksize,
                             priv->stride, ctx->u + offset, ctx->rhs + offset,
                             diff_coeffs, priv->fd_factors);
}

static void residual_calc(EllRelaxContext *ctx)
{
    EllRelaxInternal *priv = ctx->priv;
    double res_max = 0.0;
    int64_t start;

    memset(priv->residual_max, 0, sizeof(*priv->residual_max) * priv->residual_max_size);

    start = gettime();

    tp_execute(ctx->tp, priv->residual_calc_size[1], residual_calc_task, ctx);

    for (size_t i = 0; i < priv->residual_max_size; i++)
        res_max = MAX(res_max, priv->residual_max[i]);
    ctx->residual_max = res_max;

    ctx->time_res_calc += gettime() - start;
    ctx->count_res++;
}

static void boundaries_apply_fixval(double *dst, const ptrdiff_t dst_stride[2],
                                    const double *src, ptrdiff_t src_stride,
                                    size_t boundary_size)
{
    for (int j = 0; j < FD_STENCIL_MAX; j++) {
        for (ptrdiff_t i = -j; i < (ptrdiff_t)boundary_size + j; i++)
            dst[i * dst_stride[0]] = src[i];
        dst += dst_stride[1];
        src += src_stride;
    }
}

static void boundaries_apply_fixdiff(double *dst, const ptrdiff_t dst_stride[2],
                                     const double *src, ptrdiff_t src_stride,
                                     size_t boundary_size)
{
    for (size_t i = 0; i < boundary_size; i++) {
        for (int j = 1; j <= FD_STENCIL_MAX; j++)
            dst[dst_stride[1] * j] = dst[-dst_stride[1] * j];

        dst += dst_stride[0];
    }
}

static void boundaries_apply(EllRelaxContext *ctx)
{
    EllRelaxInternal *priv = ctx->priv;
    const ptrdiff_t strides[2] = { 1, priv->stride };
    int64_t start;

    start = gettime();
    for (int i = 0; i < ARRAY_ELEMS(ctx->boundaries); i++) {
        const int si = boundary_def[i].stride_idx;
        const ptrdiff_t stride_boundary = strides[si];
        const ptrdiff_t stride_offset   = strides[!si];
        const size_t size_boundary      = ctx->domain_size[si];
        const size_t size_offset        = ctx->domain_size[!si];

        double *dst = ctx->u + boundary_def[i].is_upper * ((size_offset - 1) * stride_offset);
        const ptrdiff_t dst_strides[] = { stride_boundary,
            (boundary_def[i].is_upper ? 1 : -1) * stride_offset };

        switch (ctx->boundaries[i]->type) {
        case MG2D_BC_TYPE_FIXVAL:
            boundaries_apply_fixval(dst, dst_strides, ctx->boundaries[i]->val,
                                    ctx->boundaries[i]->val_stride, size_boundary);
            break;
        case MG2D_BC_TYPE_FIXDIFF:
            boundaries_apply_fixdiff(dst, dst_strides, ctx->boundaries[i]->val,
                                     ctx->boundaries[i]->val_stride, size_boundary);
            break;
        }
    }

    /* fill in the corner ghosts */
    if (ctx->boundaries[MG2D_BOUNDARY_0L]->type == MG2D_BC_TYPE_FIXDIFF ||
        ctx->boundaries[MG2D_BOUNDARY_1L]->type == MG2D_BC_TYPE_FIXDIFF) {
        double *dst = ctx->u;
        int fact_x = -1, fact_z = -1;

        if (ctx->boundaries[MG2D_BOUNDARY_0L]->type == MG2D_BC_TYPE_FIXDIFF)
            fact_z *= -1;
        else
            fact_x *= -1;

        for (int i = 1; i <= FD_STENCIL_MAX; i++)
            for (int j = 1; j <= FD_STENCIL_MAX; j++) {
                const ptrdiff_t idx_dst = -j * strides[1] - i;
                const ptrdiff_t idx_src = fact_z * j * strides[1] + fact_x * i;
                dst[idx_dst] = dst[idx_src];
            }
    }
    if (ctx->boundaries[MG2D_BOUNDARY_0L]->type == MG2D_BC_TYPE_FIXDIFF ||
        ctx->boundaries[MG2D_BOUNDARY_1U]->type == MG2D_BC_TYPE_FIXDIFF) {
        double *dst = ctx->u + ctx->domain_size[0] - 1;
        int fact_x = 1, fact_z = -1;

        if (ctx->boundaries[MG2D_BOUNDARY_0L]->type == MG2D_BC_TYPE_FIXDIFF)
            fact_z *= -1;
        else
            fact_x *= -1;

        for (int i = 1; i <= FD_STENCIL_MAX; i++)
            for (int j = 1; j <= FD_STENCIL_MAX; j++) {
                const ptrdiff_t idx_dst = -j * strides[1] + i;
                const ptrdiff_t idx_src = fact_z * j * strides[1] + fact_x * i;
                dst[idx_dst] = dst[idx_src];
            }
    }
    if (ctx->boundaries[MG2D_BOUNDARY_1L]->type == MG2D_BC_TYPE_FIXDIFF ||
        ctx->boundaries[MG2D_BOUNDARY_0U]->type == MG2D_BC_TYPE_FIXDIFF) {
        double *dst = ctx->u + strides[1] * (ctx->domain_size[1] - 1);
        int fact_x = -1, fact_z = 1;

        if (ctx->boundaries[MG2D_BOUNDARY_0U]->type == MG2D_BC_TYPE_FIXDIFF)
            fact_z *= -1;
        else
            fact_x *= -1;

        for (int i = 1; i <= FD_STENCIL_MAX; i++)
            for (int j = 1; j <= FD_STENCIL_MAX; j++) {
                const ptrdiff_t idx_dst = j * strides[1] - i;
                const ptrdiff_t idx_src = fact_z * j * strides[1] + fact_x * i;
                dst[idx_dst] = dst[idx_src];
            }
    }
    if (ctx->boundaries[MG2D_BOUNDARY_0U]->type == MG2D_BC_TYPE_FIXDIFF ||
        ctx->boundaries[MG2D_BOUNDARY_1U]->type == MG2D_BC_TYPE_FIXDIFF) {
        double *dst = ctx->u + strides[1] * (ctx->domain_size[1] - 1) + ctx->domain_size[0] - 1;
        int fact_x = 1, fact_z = 1;

        if (ctx->boundaries[MG2D_BOUNDARY_0U]->type == MG2D_BC_TYPE_FIXDIFF)
            fact_z *= -1;
        else
            fact_x *= -1;

        for (int i = 1; i <= FD_STENCIL_MAX; i++)
            for (int j = 1; j <= FD_STENCIL_MAX; j++) {
                const ptrdiff_t idx_dst = j * strides[1] + i;
                const ptrdiff_t idx_src = fact_z * j * strides[1] + fact_x * i;
                dst[idx_dst] = dst[idx_src];
            }
    }
    ctx->time_boundaries += gettime() - start;
    ctx->count_boundaries++;
}

static void residual_add_task(void *arg, unsigned int job_idx, unsigned int thread_idx)
{
    EllRelaxContext   *ctx = arg;
    EllRelaxInternal *priv = ctx->priv;
    ptrdiff_t offset = job_idx * priv->stride;

    for (int idx0 = 0; idx0 < ctx->domain_size[0]; idx0++) {
        ptrdiff_t idx = job_idx * ctx->u_stride + idx0;

        ctx->u[idx] += priv->relax_factor * ctx->residual[idx];
    }
}

int mg2di_ell_relax_step(EllRelaxContext *ctx)
{
    EllRelaxInternal *priv = ctx->priv;
    const double cfl_fac = priv->relax_factor;
    int64_t start;

    start = gettime();

    tp_execute(ctx->tp, ctx->domain_size[1], residual_add_task, ctx);

    ctx->time_correct += gettime() - start;
    ctx->count_correct++;

    boundaries_apply(ctx);
    residual_calc(ctx);

    return 0;
}

int mg2di_ell_relax_init(EllRelaxContext *ctx)
{
    EllRelaxInternal *priv = ctx->priv;
    double *tmp;
    int ret;

    priv->calc_blocksize = 1;
    switch (ctx->fd_stencil) {
    case 1:
        priv->residual_calc_line = residual_calc_line_s1_c;
#if HAVE_EXTERNAL_ASM
        if (ctx->cpuflags & MG2DI_CPU_FLAG_FMA3) {
            priv->residual_calc_line = mg2di_residual_calc_line_s1_fma3;
            priv->calc_blocksize     = 4;
        }
#endif
        break;
    case 2:
        priv->residual_calc_line = residual_calc_line_s2_c;
#if HAVE_EXTERNAL_ASM
        if (ctx->cpuflags & MG2DI_CPU_FLAG_FMA3) {
            priv->residual_calc_line = mg2di_residual_calc_line_s2_fma3;
            priv->calc_blocksize     = 4;
        }
#endif
        break;
    default:
        mg2di_log(&ctx->logger, 0, "Invalid finite difference stencil: %zd\n",
                  ctx->fd_stencil);
        return -EINVAL;
    }

    if (ctx->step[0] <= DBL_EPSILON || ctx->step[1] <= DBL_EPSILON) {
        mg2di_log(&ctx->logger, 0, "Spatial step size too small\n");
        return -EINVAL;
    }

    if (ctx->relax_factor == 0.0)
        priv->relax_factor = relax_factors[ctx->fd_stencil - 1];
    else
        priv->relax_factor = ctx->relax_factor;
    priv->relax_factor *= ctx->step[0] * ctx->step[0];

    priv->fd_factors[MG2D_DIFF_COEFF_00] = 1.0 /  fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_00];
    priv->fd_factors[MG2D_DIFF_COEFF_10] = 1.0 / (fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_10] * ctx->step[0]);
    priv->fd_factors[MG2D_DIFF_COEFF_01] = 1.0 / (fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_01] * ctx->step[1]);
    priv->fd_factors[MG2D_DIFF_COEFF_20] = 1.0 / (fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_20] * SQR(ctx->step[0]));
    priv->fd_factors[MG2D_DIFF_COEFF_02] = 1.0 / (fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_02] * SQR(ctx->step[1]));
    priv->fd_factors[MG2D_DIFF_COEFF_11] = 1.0 / (fd_denoms[ctx->fd_stencil - 1][MG2D_DIFF_COEFF_11] * ctx->step[0] * ctx->step[1]);

    if (!ctx->tp) {
        ret = tp_init(&priv->tp_internal, 1);
        if (ret < 0)
            return ret;
        ctx->tp = priv->tp_internal;
    }

    priv->residual_calc_offset  = 0;
    priv->residual_calc_size[0] = ctx->domain_size[0];
    priv->residual_calc_size[1] = ctx->domain_size[1];
    if (ctx->boundaries[MG2D_BOUNDARY_0L]->type == MG2D_BC_TYPE_FIXVAL)
        priv->residual_calc_offset += ctx->residual_stride;
    if (ctx->boundaries[MG2D_BOUNDARY_1L]->type == MG2D_BC_TYPE_FIXVAL)
        priv->residual_calc_offset++;

    for (int i = 0; i < ARRAY_ELEMS(ctx->boundaries); i++) {
        MG2DBoundary *bnd = ctx->boundaries[i];
        if (bnd->type == MG2D_BC_TYPE_FIXDIFF) {
           for (int k = 0; k < ctx->domain_size[boundary_def[i].stride_idx]; k++)
               if (bnd->val[k] != 0.0) {
                   mg2di_log(&ctx->logger, 0, "Only zero boundary derivative supported\n");
                   return -ENOSYS;
               }
        } else if (bnd->type == MG2D_BC_TYPE_FIXVAL) {
            priv->residual_calc_size[!boundary_def[i].stride_idx]--;
        }
    }

    priv->residual_max_size = tp_get_nb_threads(ctx->tp) * priv->calc_blocksize;
    tmp = realloc(priv->residual_max,
                  sizeof(*priv->residual_max) * priv->residual_max_size);
    if (!tmp) {
        priv->residual_max_size = 0;
        return -ENOMEM;
    }
    priv->residual_max = tmp;

    boundaries_apply(ctx);
    residual_calc(ctx);

    return 0;
}

static int ell_relax_arrays_alloc(EllRelaxContext *ctx, const size_t domain_size[2])
{
    EllRelaxInternal *priv = ctx->priv;

    const size_t ghosts = FD_STENCIL_MAX;
    const size_t size_padded[2] = {
        domain_size[0] + 2 * ghosts,
        domain_size[1] + 2 * ghosts,
    };
    const size_t stride = size_padded[0];
    const size_t start_offset = ghosts * stride + ghosts;
    const size_t arr_size = size_padded[0] * size_padded[1];
    int ret;

    ret = posix_memalign((void**)&priv->u_base, 32, sizeof(*priv->u_base) * arr_size);
    if (ret != 0)
        return -ret;
    ctx->u        = priv->u_base + start_offset;
    ctx->u_stride = stride;

    ret = posix_memalign((void**)&priv->rhs_base, 32, sizeof(*priv->rhs_base) * arr_size);
    if (ret != 0)
        return -ret;
    ctx->rhs        = priv->rhs_base + start_offset;
    ctx->rhs_stride = stride;

    ret = posix_memalign((void**)&priv->residual_base, 32, sizeof(*priv->residual_base) * arr_size);
    if (ret != 0)
        return -ret;
    memset(priv->residual_base, 0, sizeof(*priv->residual_base) * arr_size);
    ctx->residual        = priv->residual_base + start_offset;
    ctx->residual_stride = stride;

    for (int i = 0; i < ARRAY_ELEMS(ctx->diff_coeffs); i++) {
        ret = posix_memalign((void**)&priv->diff_coeffs_base[i], 32,
                             sizeof(*priv->diff_coeffs_base[i]) * arr_size);
        if (ret != 0)
            return -ret;
        ctx->diff_coeffs[i] = priv->diff_coeffs_base[i] + start_offset;
    }
    ctx->diff_coeffs_stride = stride;

    priv->stride = stride;

    for (int i = 0; i < ARRAY_ELEMS(ctx->boundaries); i++) {
        ctx->boundaries[i] = mg2di_bc_alloc(domain_size[boundary_def[i].stride_idx]);
        if (!ctx->boundaries[i])
            return -ENOMEM;
    }

    return 0;
}

EllRelaxContext *mg2di_ell_relax_alloc(size_t domain_size[2])
{
    EllRelaxContext *ctx;
    EllRelaxInternal *priv;
    int ret;

    ctx = calloc(1, sizeof(*ctx));
    if (!ctx)
        return NULL;

    ctx->priv = calloc(1, sizeof(*ctx->priv));
    if (!ctx->priv)
        goto fail;
    priv = ctx->priv;

    if (!domain_size[0] || !domain_size[1] ||
        domain_size[0] > SIZE_MAX / domain_size[1])
        goto fail;

    ret = ell_relax_arrays_alloc(ctx, domain_size);
    if (ret < 0)
        goto fail;

    ctx->domain_size[0] = domain_size[0];
    ctx->domain_size[1] = domain_size[1];

    return ctx;
fail:
    mg2di_ell_relax_free(&ctx);
    return NULL;
}

void mg2di_ell_relax_free(EllRelaxContext **pctx)
{
    EllRelaxContext *ctx = *pctx;

    if (!ctx)
        return;

    free(ctx->priv->u_base);
    free(ctx->priv->rhs_base);
    free(ctx->priv->residual_base);
    free(ctx->priv->residual_max);
    for (int i = 0; i < ARRAY_ELEMS(ctx->priv->diff_coeffs_base); i++)
        free(ctx->priv->diff_coeffs_base[i]);
    for (int i = 0; i < ARRAY_ELEMS(ctx->boundaries); i++)
        mg2di_bc_free(&ctx->boundaries[i]);

    tp_free(&ctx->priv->tp_internal);
    free(ctx->priv);

    free(ctx);
    *pctx = NULL;
}