void lpx_get_row_info(glp_prob *lp, int i, int *tagx, double *vx, double *dx) { /* obtain row solution information */ if (tagx != NULL) *tagx = lpx_get_row_stat(lp, i); if (vx != NULL) *vx = lpx_get_row_prim(lp, i); if (dx != NULL) *dx = lpx_get_row_dual(lp, i); return; }
int lpx_prim_ratio_test(LPX *lp, int len, const int ind[], const double val[], int how, double tol) { int i, k, m, n, p, t, typx, tagx; double alfa_i, abs_alfa_i, big, eps, bbar_i, lb_i, ub_i, temp, teta; if (!lpx_is_b_avail(lp)) xfault("lpx_prim_ratio_test: LP basis is not available\n"); if (lpx_get_prim_stat(lp) != LPX_P_FEAS) xfault("lpx_prim_ratio_test: current basic solution is not pri" "mal feasible\n"); if (!(how == +1 || how == -1)) xfault("lpx_prim_ratio_test: how = %d; invalid parameter\n", how); m = lpx_get_num_rows(lp); n = lpx_get_num_cols(lp); /* compute the largest absolute value of the specified influence coefficients */ big = 0.0; for (t = 1; t <= len; t++) { temp = val[t]; if (temp < 0.0) temp = - temp; if (big < temp) big = temp; } /* compute the absolute tolerance eps used to skip small entries of the column */ if (!(0.0 < tol && tol < 1.0)) xfault("lpx_prim_ratio_test: tol = %g; invalid tolerance\n", tol); eps = tol * (1.0 + big); /* initial settings */ p = 0, teta = DBL_MAX, big = 0.0; /* walk through the entries of the specified column */ for (t = 1; t <= len; t++) { /* get the ordinal number of basic variable */ k = ind[t]; if (!(1 <= k && k <= m+n)) xfault("lpx_prim_ratio_test: ind[%d] = %d; variable number " "out of range\n", t, k); if (k <= m) tagx = lpx_get_row_stat(lp, k); else tagx = lpx_get_col_stat(lp, k-m); if (tagx != LPX_BS) xfault("lpx_prim_ratio_test: ind[%d] = %d; non-basic variab" "le not allowed\n", t, k); /* determine index of the variable x[k] in the vector xB */ if (k <= m) i = lpx_get_row_b_ind(lp, k); else i = lpx_get_col_b_ind(lp, k-m); xassert(1 <= i && i <= m); /* determine unscaled bounds and value of the basic variable xB[i] in the current basic solution */ if (k <= m) { typx = lpx_get_row_type(lp, k); lb_i = lpx_get_row_lb(lp, k); ub_i = lpx_get_row_ub(lp, k); bbar_i = lpx_get_row_prim(lp, k); } else { typx = lpx_get_col_type(lp, k-m); lb_i = lpx_get_col_lb(lp, k-m); ub_i = lpx_get_col_ub(lp, k-m); bbar_i = lpx_get_col_prim(lp, k-m); } /* determine influence coefficient for the basic variable x[k] = xB[i] in the explicitly specified column and turn to the case of increasing the variable y in order to simplify the program logic */ alfa_i = (how > 0 ? +val[t] : -val[t]); abs_alfa_i = (alfa_i > 0.0 ? +alfa_i : -alfa_i); /* analyze main cases */ switch (typx) { case LPX_FR: /* xB[i] is free variable */ continue; case LPX_LO: lo: /* xB[i] has an lower bound */ if (alfa_i > - eps) continue; temp = (lb_i - bbar_i) / alfa_i; break; case LPX_UP: up: /* xB[i] has an upper bound */ if (alfa_i < + eps) continue; temp = (ub_i - bbar_i) / alfa_i; break; case LPX_DB: /* xB[i] has both lower and upper bounds */ if (alfa_i < 0.0) goto lo; else goto up; case LPX_FX: /* xB[i] is fixed variable */ if (abs_alfa_i < eps) continue; temp = 0.0; break; default: xassert(typx != typx); } /* if the value of the variable xB[i] violates its lower or upper bound (slightly, because the current basis is assumed to be primal feasible), temp is negative; we can think this happens due to round-off errors and the value is exactly on the bound; this allows replacing temp by zero */ if (temp < 0.0) temp = 0.0; /* apply the minimal ratio test */ if (teta > temp || teta == temp && big < abs_alfa_i) p = k, teta = temp, big = abs_alfa_i; } /* return the ordinal number of the chosen basic variable */ return p; }