double glpk_wrapper::get_row_value(int i) {
double cstr_value = 0;
if (solver_type == SIMPLEX || solver_type == EXACT) {
int cstr_status = glp_get_row_stat(lp, i);
if (cstr_status == GLP_BS) { // basic variable;
cstr_status = glp_get_row_prim(lp, i); // or glp_get_row_dual
} else if (cstr_status == GLP_NL || cstr_status == GLP_NS) { // non-basic variable on its lower bound, non-basic fixed variable.
cstr_value = glp_get_row_lb(lp, i);
} else if (cstr_status == GLP_NU) { // non-basic variable on its upper bound
cstr_value = glp_get_row_ub(lp, i);
}
// TODO(dzufferey): should we do something for GLP_NF — non-basic free (unbounded) variable;
} else {
cstr_value = glp_ipt_row_prim(lp, i); // or glp_ipt_row_dual
}
return cstr_value;
}
int glp_mpl_postsolve(glp_tran *tran, glp_prob *prob, int sol)
{ /* postsolve the model */
int i, j, m, n, stat, ret;
double prim, dual;
if (!(tran->phase == 3 && !tran->flag_p))
xerror("glp_mpl_postsolve: invalid call sequence\n");
if (!(sol == GLP_SOL || sol == GLP_IPT || sol == GLP_MIP))
xerror("glp_mpl_postsolve: sol = %d; invalid parameter\n",
sol);
m = mpl_get_num_rows(tran);
n = mpl_get_num_cols(tran);
if (!(m == glp_get_num_rows(prob) &&
n == glp_get_num_cols(prob)))
xerror("glp_mpl_postsolve: wrong problem object\n");
if (!mpl_has_solve_stmt(tran))
{ ret = 0;
goto done;
}
for (i = 1; i <= m; i++)
{ if (sol == GLP_SOL)
{ stat = glp_get_row_stat(prob, i);
prim = glp_get_row_prim(prob, i);
dual = glp_get_row_dual(prob, i);
}
else if (sol == GLP_IPT)
{ stat = 0;
prim = glp_ipt_row_prim(prob, i);
dual = glp_ipt_row_dual(prob, i);
}
else if (sol == GLP_MIP)
{ stat = 0;
prim = glp_mip_row_val(prob, i);
dual = 0.0;
}
else
xassert(sol != sol);
if (fabs(prim) < 1e-9) prim = 0.0;
if (fabs(dual) < 1e-9) dual = 0.0;
mpl_put_row_soln(tran, i, stat, prim, dual);
}
for (j = 1; j <= n; j++)
{ if (sol == GLP_SOL)
{ stat = glp_get_col_stat(prob, j);
prim = glp_get_col_prim(prob, j);
dual = glp_get_col_dual(prob, j);
}
else if (sol == GLP_IPT)
{ stat = 0;
prim = glp_ipt_col_prim(prob, j);
dual = glp_ipt_col_dual(prob, j);
}
else if (sol == GLP_MIP)
{ stat = 0;
prim = glp_mip_col_val(prob, j);
dual = 0.0;
}
else
xassert(sol != sol);
if (fabs(prim) < 1e-9) prim = 0.0;
if (fabs(dual) < 1e-9) dual = 0.0;
mpl_put_col_soln(tran, j, stat, prim, dual);
}
ret = mpl_postsolve(tran);
if (ret == 3)
ret = 0;
else if (ret == 4)
ret = 1;
done: return ret;
}
double lpx_get_row_prim(LPX *lp, int i)
{ /* retrieve row primal value (basic solution) */
return glp_get_row_prim(lp, i);
}
/*
R is the random contraint data in row major memory layout
ridx is an N array of integers
soln is an array of length (n+1) soln[n] is t (objective value)
active_constr is an N-length 0-1 array
*/
void solve_lp(int N, int n, double* R, int* ridx, double* soln, int* active_constr)
{
double tol = 1.0e-14;
int size = (N+1)*(n+1) + 1; // We add one because GLPK indexes arrays
// starting at 1 instead of 0.
glp_prob *lp;
int* ia = malloc(size * sizeof(int));
int* ja = malloc(size * sizeof(int));
double* ar = malloc(size * sizeof(double));
int i, j;
lp = glp_create_prob();
glp_set_prob_name(lp, "portfolio");
glp_set_obj_dir(lp, GLP_MAX);
glp_add_rows(lp, N+1);
// Sampled constraints are ">= 0"
for (i = 1; i <= N; i++) {
glp_set_row_bnds(lp, i, GLP_LO, 0.0, 0.0);
}
// Sum = 1 constraint
glp_set_row_name(lp, N+1, "sum");
glp_set_row_bnds(lp, N+1, GLP_FX, 1.0, 1.0);
glp_add_cols(lp, n+1);
// Nonnegative variables y
for (i = 1; i <= n; i++) {
glp_set_col_bnds(lp, i, GLP_LO, 0.0, 0.0);
glp_set_obj_coef(lp, i, 0.0);
}
// Free variable t
glp_set_col_name(lp, n+1, "t");
glp_set_col_bnds(lp, n+1, GLP_FR, 0.0, 0.0);
glp_set_obj_coef(lp, n+1, 1.0);
// for (i = 0; i < N*(n-1); i++) {
// printf("%d: %g\n", i, R[i]);
// }
int idx = 1;
// Sampled constraints
for (i = 1; i <= N; i++) {
// Uncertain assets
for (j = 1; j < n; j++) {
ia[idx] = i;
ja[idx] = j;
ar[idx] = R[ ridx[(i-1)] * (n-1) + (j-1) ];
idx += 1;
}
// Fixed return asset
ia[idx] = i;
ja[idx] = n;
ar[idx] = 1.05;
idx += 1;
// t
ia[idx] = i;
ja[idx] = n+1;
ar[idx] = -1.0;
idx += 1;
}
// Sum = 1 constraint
for (i = 1; i <= n; i++) {
ia[idx] = N+1;
ja[idx] = i;
ar[idx] = 1.0;
idx += 1;
}
// t
ia[idx] = N+1;
ja[idx] = n+1;
ar[idx] = 0.0;
idx += 1;
// for (i = 1; i < size; i++) {
// printf("%d %d %g\n", ia[i], ja[i], ar[i]);
// }
glp_load_matrix(lp, size-1, ia, ja, ar);
// glp_scale_prob(lp, GLP_SF_AUTO);
glp_smcp param;
glp_init_smcp(¶m);
param.meth = GLP_PRIMAL;
//glp_std_basis(lp);
glp_simplex(lp, ¶m);
double z = glp_get_obj_val(lp);
// printf("z = %g\n", z);
if (soln) {
for (i = 0; i < n; i++) {
double y = glp_get_col_prim(lp, i+1);
soln[i] = y;
// printf("y%d = %g\n", i, y);
}
double t = glp_get_col_prim(lp, n+1);
soln[n] = t;
// printf("t = %g\n", glp_get_col_prim(lp, n+1));
}
for (i = 1; i <= N; i++) {
double slack = glp_get_row_prim(lp, i);
active_constr[i-1] = fabs(slack) < tol ? 1 : 0;
// printf("constr%d %d\n", i, active_constr[i-1]);
}
glp_delete_prob(lp);
// glp_free_env();
free(ia);
free(ja);
free(ar);
}
double c_glp_get_row_prim(glp_prob *lp, int i){
return glp_get_row_prim(lp, i);
}