/* Copyright (C) 2005, 2006 International Business Machines and others.
 * All Rights Reserved.
 * This code is published under the Common Public License.
 *
 * $Id: hs071_c.c 1324 2008-09-16 14:19:26Z andreasw $
 *
 * Authors:  Carl Laird, Andreas Waechter     IBM    2005-08-17
 */

#include "IpStdCInterface.h"
#include <stdlib.h>
#include <assert.h>
#include <stdio.h>

/* Function Declarations */
Bool eval_f(Index n, Number* x, Bool new_x,
            Number* obj_value, UserDataPtr user_data);

Bool eval_grad_f(Index n, Number* x, Bool new_x,
                 Number* grad_f, UserDataPtr user_data);

Bool eval_g(Index n, Number* x, Bool new_x,
            Index m, Number* g, UserDataPtr user_data);

Bool eval_jac_g(Index n, Number *x, Bool new_x,
                Index m, Index nele_jac,
                Index *iRow, Index *jCol, Number *values,
                UserDataPtr user_data);

Bool eval_h(Index n, Number *x, Bool new_x, Number obj_factor,
            Index m, Number *lambda, Bool new_lambda,
            Index nele_hess, Index *iRow, Index *jCol,
            Number *values, UserDataPtr user_data);

/* Main Program */
int main()
{
  Index n=-1;                          /* number of variables */
  Index m=-1;                          /* number of constraints */
  Number* x_L = NULL;                  /* lower bounds on x */
  Number* x_U = NULL;                  /* upper bounds on x */
  Number* g_L = NULL;                  /* lower bounds on g */
  Number* g_U = NULL;                  /* upper bounds on g */
  IpoptProblem nlp = NULL;             /* IpoptProblem */
  enum ApplicationReturnStatus status; /* Solve return code */
  Number* x = NULL;                    /* starting point and solution vector */
  Number* mult_x_L = NULL;             /* lower bound multipliers
  					  at the solution */
  Number* mult_x_U = NULL;             /* upper bound multipliers
  					  at the solution */
  Number obj;                          /* objective value */
  Index i;                             /* generic counter */

  /* Number of nonzeros in the Jacobian of the constraints */
  Index nele_jac = 8;
  /* Number of nonzeros in the Hessian of the Lagrangian (lower or
     upper triangual part only) */
  Index nele_hess = 10;
  /* indexing style for matrices */
  Index index_style = 0; /* C-style; start counting of rows and column
  			    indices at 0 */

  /* set the number of variables and allocate space for the bounds */
  n=4;
  x_L = (Number*)malloc(sizeof(Number)*n);
  x_U = (Number*)malloc(sizeof(Number)*n);
  /* set the values for the variable bounds */
  for (i=0; i<n; i++) {
    x_L[i] = 1.0;
    x_U[i] = 5.0;
  }

  /* set the number of constraints and allocate space for the bounds */
  m=2;
  g_L = (Number*)malloc(sizeof(Number)*m);
  g_U = (Number*)malloc(sizeof(Number)*m);
  /* set the values of the constraint bounds */
  g_L[0] = 25;
  g_U[0] = 2e19;
  g_L[1] = 40;
  g_U[1] = 40;

  /* create the IpoptProblem */
  nlp = CreateIpoptProblem(n, x_L, x_U, m, g_L, g_U, nele_jac, nele_hess,
                           index_style, &eval_f, &eval_g, &eval_grad_f,
                           &eval_jac_g, &eval_h);

  /* We can free the memory now - the values for the bounds have been
     copied internally in CreateIpoptProblem */
  free(x_L);
  free(x_U);
  free(g_L);
  free(g_U);

  /* Set some options.  Note the following ones are only examples,
     they might not be suitable for your problem. */
  AddIpoptNumOption(nlp, "tol", 1e-7);
  AddIpoptStrOption(nlp, "mu_strategy", "adaptive");
  AddIpoptStrOption(nlp, "output_file", "ipopt.out");

  /* allocate space for the initial point and set the values */
  x = (Number*)malloc(sizeof(Number)*n);
  x[0] = 1.0;
  x[1] = 5.0;
  x[2] = 5.0;
  x[3] = 1.0;

  /* allocate space to store the bound multipliers at the solution */
  mult_x_L = (Number*)malloc(sizeof(Number)*n);
  mult_x_U = (Number*)malloc(sizeof(Number)*n);

  /* solve the problem */
  status = IpoptSolve(nlp, x, NULL, &obj, NULL, mult_x_L, mult_x_U, NULL);

  if (status == Solve_Succeeded) {
    printf("\n\nSolution of the primal variables, x\n");
    for (i=0; i<n; i++) {
      printf("x[%d] = %e\n", i, x[i]);
    }

    printf("\n\nSolution of the bound multipliers, z_L and z_U\n");
    for (i=0; i<n; i++) {
      printf("z_L[%d] = %e\n", i, mult_x_L[i]);
    }
    for (i=0; i<n; i++) {
      printf("z_U[%d] = %e\n", i, mult_x_U[i]);
    }

    printf("\n\nObjective value\n");
    printf("f(x*) = %e\n", obj);
  }

  /* free allocated memory */
  FreeIpoptProblem(nlp);
  free(x);
  free(mult_x_L);
  free(mult_x_U);

  return 0;
}


/* Function Implementations */
Bool eval_f(Index n, Number* x, Bool new_x,
            Number* obj_value, UserDataPtr user_data)
{
  assert(n == 4);

  *obj_value = x[0] * x[3] * (x[0] + x[1] + x[2]) + x[2];

  return TRUE;
}

Bool eval_grad_f(Index n, Number* x, Bool new_x,
                 Number* grad_f, UserDataPtr user_data)
{
  assert(n == 4);

  grad_f[0] = x[0] * x[3] + x[3] * (x[0] + x[1] + x[2]);
  grad_f[1] = x[0] * x[3];
  grad_f[2] = x[0] * x[3] + 1;
  grad_f[3] = x[0] * (x[0] + x[1] + x[2]);

  return TRUE;
}

Bool eval_g(Index n, Number* x, Bool new_x,
            Index m, Number* g, UserDataPtr user_data)
{
  assert(n == 4);
  assert(m == 2);

  g[0] = x[0] * x[1] * x[2] * x[3];
  g[1] = x[0]*x[0] + x[1]*x[1] + x[2]*x[2] + x[3]*x[3];

  return TRUE;
}

Bool eval_jac_g(Index n, Number *x, Bool new_x,
                Index m, Index nele_jac,
                Index *iRow, Index *jCol, Number *values,
                UserDataPtr user_data)
{
  if (values == NULL) {
    /* return the structure of the jacobian */

    /* this particular jacobian is dense */
    iRow[0] = 0;
    jCol[0] = 0;
    iRow[1] = 0;
    jCol[1] = 1;
    iRow[2] = 0;
    jCol[2] = 2;
    iRow[3] = 0;
    jCol[3] = 3;
    iRow[4] = 1;
    jCol[4] = 0;
    iRow[5] = 1;
    jCol[5] = 1;
    iRow[6] = 1;
    jCol[6] = 2;
    iRow[7] = 1;
    jCol[7] = 3;
  }
  else {
    /* return the values of the jacobian of the constraints */

    values[0] = x[1]*x[2]*x[3]; /* 0,0 */
    values[1] = x[0]*x[2]*x[3]; /* 0,1 */
    values[2] = x[0]*x[1]*x[3]; /* 0,2 */
    values[3] = x[0]*x[1]*x[2]; /* 0,3 */

    values[4] = 2*x[0];         /* 1,0 */
    values[5] = 2*x[1];         /* 1,1 */
    values[6] = 2*x[2];         /* 1,2 */
    values[7] = 2*x[3];         /* 1,3 */
  }

  return TRUE;
}

Bool eval_h(Index n, Number *x, Bool new_x, Number obj_factor,
            Index m, Number *lambda, Bool new_lambda,
            Index nele_hess, Index *iRow, Index *jCol,
            Number *values, UserDataPtr user_data)
{
  Index idx = 0; /* nonzero element counter */
  Index row = 0; /* row counter for loop */
  Index col = 0; /* col counter for loop */
  if (values == NULL) {
    /* return the structure. This is a symmetric matrix, fill the lower left
     * triangle only. */

    /* the hessian for this problem is actually dense */
    idx=0;
    for (row = 0; row < 4; row++) {
      for (col = 0; col <= row; col++) {
        iRow[idx] = row;
        jCol[idx] = col;
        idx++;
      }
    }

    assert(idx == nele_hess);
  }
  else {
    /* return the values. This is a symmetric matrix, fill the lower left
     * triangle only */

    /* fill the objective portion */
    values[0] = obj_factor * (2*x[3]);               /* 0,0 */

    values[1] = obj_factor * (x[3]);                 /* 1,0 */
    values[2] = 0;                                   /* 1,1 */

    values[3] = obj_factor * (x[3]);                 /* 2,0 */
    values[4] = 0;                                   /* 2,1 */
    values[5] = 0;                                   /* 2,2 */

    values[6] = obj_factor * (2*x[0] + x[1] + x[2]); /* 3,0 */
    values[7] = obj_factor * (x[0]);                 /* 3,1 */
    values[8] = obj_factor * (x[0]);                 /* 3,2 */
    values[9] = 0;                                   /* 3,3 */


    /* add the portion for the first constraint */
    values[1] += lambda[0] * (x[2] * x[3]);          /* 1,0 */

    values[3] += lambda[0] * (x[1] * x[3]);          /* 2,0 */
    values[4] += lambda[0] * (x[0] * x[3]);          /* 2,1 */

    values[6] += lambda[0] * (x[1] * x[2]);          /* 3,0 */
    values[7] += lambda[0] * (x[0] * x[2]);          /* 3,1 */
    values[8] += lambda[0] * (x[0] * x[1]);          /* 3,2 */

    /* add the portion for the second constraint */
    values[0] += lambda[1] * 2;                      /* 0,0 */

    values[2] += lambda[1] * 2;                      /* 1,1 */

    values[5] += lambda[1] * 2;                      /* 2,2 */

    values[9] += lambda[1] * 2;                      /* 3,3 */
  }

  return TRUE;
}
