/* Copyright (c) 2012, NVIDIA CORPORATION. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * 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.
 *  * Neither the name of NVIDIA CORPORATION nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``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 ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <math.h>
#include <string.h>
#include <stdlib.h>
#include <omp.h>
#include <stdio.h>

double simplest_checksum(int imax, int jmax, double (*in)[jmax+2]) {
  double checksum = 0.0;
  int i;
  int j;
  for (i=1; i<(imax+1); i++){
    for (j=1; j<(jmax+1); j++){
      checksum+=in[i][j]*((double)((i)*jmax)+(j));
    }
  }

  return checksum;
}

void print_file(int imax, int jmax, double (*in)[jmax+2]) {
  char fname[10];
  sprintf(fname,"out.txt");
  FILE *f=fopen(fname,"w");
  int i;
  int j;
  for (i=0; i<(imax+2); i++){
    for (j=0; j<(jmax+2); j++){
      fprintf(f,"%g ",in[i][j]);
    }
    fprintf(f,"\n");
  }
  fclose(f);
}

void func(int imax, int jmax, double (*restrict A)[jmax+2], double (*restrict Anew)[jmax+2]) {
    #pragma acc parallel loop present(A,Anew) collapse(2)
    for( int i = 1; i < imax+1; i++ )
        {
            for( int j = 1; j < jmax+1; j++)
            {
                A[i][j] = Anew[i][j];
            }
        }
}

int main(int argc, char** argv)
{
    //Size along y
    int jmax = 4094;
    //Size along x
    int imax = 4094;
    int iter_max = 1000;

    const double pi  = 2.0 * asin(1.0);
    const double tol = 1.0e-5;
    double error     = 1.0;

    double (*restrict A)[jmax+2];
    double (*restrict Anew)[jmax+2];
    double *restrict y0;

    A    = (double (*)[jmax+2])malloc((imax+2) * (jmax+2) * sizeof(double));
    Anew = (double (*)[jmax+2])malloc((imax+2) * (jmax+2) * sizeof(double));
    y0   = (double *)malloc((imax+2) * sizeof(double));

    memset(A, 0, (imax+2) * (jmax+2) * sizeof(double));

    // set boundary conditions
      for (int j = 0; j < jmax+2; j++)
        A[0][j]   = 0.0;

      for (int j = 0; j < jmax+2; j++)
        A[imax+1][j] = 0.0;

    for (int i = 0; i < imax+2; i++)
    {
        y0[i] = sin(pi * (i) / (imax+1));
        A[i][0] = y0[i];
    }

    for (int i = 0; i < imax+2; i++)
    {
        y0[i] = sin(pi * (i) / (imax+1));
        A[i][jmax+1] = y0[i]*exp(-pi);
    }

    printf("Jacobi relaxation Calculation: %d x %d mesh\n", imax+2, jmax+2);

    double t1 = omp_get_wtime();
    int iter = 0;

    for (int j = 1; j < jmax+2; j++)
       Anew[0][j]   = 0.0;

    for (int j = 1; j < jmax+2; j++)
       Anew[imax+1][j] = 0.0;

    for (int i = 1; i < imax+2; i++)
        Anew[i][0]   = y0[i];

    for (int i = 1; i < imax+2; i++)
        Anew[i][jmax+1] = y0[i]*expf(-pi);

    #pragma acc data copy(A[0:imax+2] [0:jmax+2], Anew[0:imax+2] [0:jmax+2])
    while ( error > tol && iter < iter_max )
    {
        error = 0.0;
        #pragma acc parallel loop reduction(max:error)
        for( int i = 1; i < imax+1; i++ )
        {
            for( int j = 1; j < jmax+1; j++)
            {
                Anew[i][j] = 0.25f * ( A[i][j+1] + A[i][j-1]
                                     + A[i-1][j] + A[i+1][j]);
                error = fmax( error, fabs(Anew[i][j]-A[i][j]));
            }
        }

        func(imax, jmax, A, Anew);

        if(iter % 100 == 0) printf("%5d, %0.8f\n", iter, error);
        iter++;
    }
    double checksum = simplest_checksum(imax,jmax,A);
    printf("Checksum: %4.8f\n",checksum);
    double runtime = omp_get_wtime()-t1;

    printf(" total: %f s\n", runtime);

    return 0;
}