basis_reduction_tab.c

   1 #include <assert.h>
   2 #include "isl_seq.h"
   3 #include "isl_tab.h"
   4
   5 struct tab_lp {
   6         struct isl_ctx  *ctx;
   7         struct isl_vec  *row;
   8         struct isl_tab  *tab;
   9         struct isl_tab_undo     **stack;
  10         isl_int         *obj;
  11         isl_int          opt;
  12         isl_int          opt_denom;
  13         isl_int          tmp;
  14         isl_int          tmp2;
  15         int              neq;
  16         unsigned         dim;
  17         /* number of constraints in initial product tableau */
  18         int              con_offset;
  19         /* objective function has fixed or no integer value */
  20         int              is_fixed;
  21 };
  22
  23 static struct tab_lp *init_lp(struct isl_tab *tab);
  24 static void set_lp_obj(struct tab_lp *lp, isl_int *row, int dim);
  25 static int solve_lp(struct tab_lp *lp);
  26 static void get_obj_val(struct tab_lp* lp, mpq_t *F);
  27 static void delete_lp(struct tab_lp *lp);
  28 static int add_lp_row(struct tab_lp *lp, isl_int *row, int dim);
  29 static void get_alpha(struct tab_lp* lp, int row, mpq_t *alpha);
  30 static int del_lp_row(struct tab_lp *lp) WARN_UNUSED;
  31 static int cut_lp_to_hyperplane(struct tab_lp *lp, isl_int *row);
  32
  33 #define GBR_LP                              struct tab_lp
  34 #define GBR_type                            mpq_t
  35 #define GBR_init(v)                         mpq_init(v)
  36 #define GBR_clear(v)                        mpq_clear(v)
  37 #define GBR_set(a,b)                        mpq_set(a,b)
  38 #define GBR_set_ui(a,b)                     mpq_set_ui(a,b,1)
  39 #define GBR_mul(a,b,c)                      mpq_mul(a,b,c)
  40 #define GBR_lt(a,b)                         (mpq_cmp(a,b) < 0)
  41 #define GBR_is_zero(a)                      (mpq_sgn(a) == 0)
  42 #define GBR_floor(a,b)                      mpz_fdiv_q(a,mpq_numref(b),mpq_denref(b))
  43 #define GBR_ceil(a,b)                       mpz_cdiv_q(a,mpq_numref(b),mpq_denref(b))
  44 #define GBR_lp_init(P)                      init_lp(P)
  45 #define GBR_lp_set_obj(lp, obj, dim)        set_lp_obj(lp, obj, dim)
  46 #define GBR_lp_solve(lp)                    solve_lp(lp)
  47 #define GBR_lp_get_obj_val(lp, F)           get_obj_val(lp, F)
  48 #define GBR_lp_delete(lp)                   delete_lp(lp)
  49 #define GBR_lp_next_row(lp)                 lp->neq
  50 #define GBR_lp_add_row(lp, row, dim)        add_lp_row(lp, row, dim)
  51 #define GBR_lp_get_alpha(lp, row, alpha)    get_alpha(lp, row, alpha)
  52 #define GBR_lp_del_row(lp)                  del_lp_row(lp)
  53 #define GBR_lp_is_fixed(lp)                 (lp)->is_fixed
  54 #define GBR_lp_cut(lp, obj)                 cut_lp_to_hyperplane(lp, obj)
  55 #include "basis_reduction_templ.c"
  56
  57 /* Set up a tableau for the Cartesian product of bset with itself.
  58  * This could be optimized by first setting up a tableau for bset
  59  * and then performing the Cartesian product on the tableau.
  60  */
  61 static struct isl_tab *gbr_tab(struct isl_tab *tab, struct isl_vec *row)
  62 {
  63         int i, j;
  64         unsigned dim;
  65         struct isl_tab *prod;
  66
  67         if (!tab || !row)
  68                 return NULL;
  69
  70         dim = tab->n_var;
  71         prod = isl_tab_product(tab, tab);
  72         if (isl_tab_extend_cons(prod, 3 * dim + 1) < 0) {
  73                 isl_tab_free(prod);
  74                 return NULL;
  75         }
  76         return prod;
  77 }
  78
  79 static struct tab_lp *init_lp(struct isl_tab *tab)
  80 {
  81         struct tab_lp *lp = NULL;
  82
  83         if (!tab)
  84                 return NULL;
  85
  86         lp = isl_calloc_type(tab->mat->ctx, struct tab_lp);
  87         if (!lp)
  88                 return NULL;
  89
  90         isl_int_init(lp->opt);
  91         isl_int_init(lp->opt_denom);
  92         isl_int_init(lp->tmp);
  93         isl_int_init(lp->tmp2);
  94
  95         lp->dim = tab->n_var;
  96
  97         lp->ctx = tab->mat->ctx;
  98         isl_ctx_ref(lp->ctx);
  99
 100         lp->stack = isl_alloc_array(lp->ctx, struct isl_tab_undo *, lp->dim);
 101
 102         lp->row = isl_vec_alloc(lp->ctx, 1 + 2 * lp->dim);
 103         if (!lp->row)
 104                 goto error;
 105         lp->tab = gbr_tab(tab, lp->row);
 106         if (!lp->tab)
 107                 goto error;
 108         lp->con_offset = lp->tab->n_con;
 109         lp->obj = NULL;
 110         lp->neq = 0;
 111
 112         return lp;
 113 error:
 114         delete_lp(lp);
 115         return NULL;
 116 }
 117
 118 static void set_lp_obj(struct tab_lp *lp, isl_int *row, int dim)
 119 {
 120         lp->obj = row;
 121 }
 122
 123 static int solve_lp(struct tab_lp *lp)
 124 {
 125         enum isl_lp_result res;
 126         unsigned flags = 0;
 127
 128         lp->is_fixed = 0;
 129
 130         isl_int_set_si(lp->row->el[0], 0);
 131         isl_seq_cpy(lp->row->el + 1, lp->obj, lp->dim);
 132         isl_seq_neg(lp->row->el + 1 + lp->dim, lp->obj, lp->dim);
 133         if (lp->neq)
 134                 flags = ISL_TAB_SAVE_DUAL;
 135         res = isl_tab_min(lp->tab, lp->row->el, lp->ctx->one,
 136                           &lp->opt, &lp->opt_denom, flags);
 137         isl_int_mul_ui(lp->opt_denom, lp->opt_denom, 2);
 138         if (isl_int_abs_lt(lp->opt, lp->opt_denom)) {
 139                 struct isl_vec *sample = isl_tab_get_sample_value(lp->tab);
 140                 if (!sample)
 141                         return -1;
 142                 isl_seq_inner_product(lp->obj, sample->el + 1, lp->dim, &lp->tmp);
 143                 isl_seq_inner_product(lp->obj, sample->el + 1 + lp->dim, lp->dim, &lp->tmp2);
 144                 isl_int_cdiv_q(lp->tmp, lp->tmp, sample->el[0]);
 145                 isl_int_fdiv_q(lp->tmp2, lp->tmp2, sample->el[0]);
 146                 if (isl_int_ge(lp->tmp, lp->tmp2))
 147                         lp->is_fixed = 1;
 148                 isl_vec_free(sample);
 149         }
 150         isl_int_divexact_ui(lp->opt_denom, lp->opt_denom, 2);
 151         if (res != isl_lp_ok)
 152                 return -1;
 153         return 0;
 154 }
 155
 156 /* The current objective function has a fixed (or no) integer value.
 157  * Cut the tableau to the hyperplane that fixes this value in
 158  * both halves of the tableau.
 159  * Return 1 if the resulting tableau is empty.
 160  */
 161 static int cut_lp_to_hyperplane(struct tab_lp *lp, isl_int *row)
 162 {
 163         enum isl_lp_result res;
 164
 165         isl_int_set_si(lp->row->el[0], 0);
 166         isl_seq_cpy(lp->row->el + 1, row, lp->dim);
 167         isl_seq_clr(lp->row->el + 1 + lp->dim, lp->dim);
 168         res = isl_tab_min(lp->tab, lp->row->el, lp->ctx->one,
 169                           &lp->tmp, NULL, 0);
 170         if (res != isl_lp_ok)
 171                 return -1;
 172
 173         isl_int_neg(lp->row->el[0], lp->tmp);
 174         lp->tab = isl_tab_add_eq(lp->tab, lp->row->el);
 175
 176         isl_seq_cpy(lp->row->el + 1 + lp->dim, row, lp->dim);
 177         isl_seq_clr(lp->row->el + 1, lp->dim);
 178         lp->tab = isl_tab_add_eq(lp->tab, lp->row->el);
 179
 180         lp->con_offset += 2;
 181
 182         return lp->tab->empty;
 183 }
 184
 185 static void get_obj_val(struct tab_lp* lp, mpq_t *F)
 186 {
 187         isl_int_neg(mpq_numref(*F), lp->opt);
 188         isl_int_set(mpq_denref(*F), lp->opt_denom);
 189 }
 190
 191 static void delete_lp(struct tab_lp *lp)
 192 {
 193         if (!lp)
 194                 return;
 195
 196         isl_int_clear(lp->opt);
 197         isl_int_clear(lp->opt_denom);
 198         isl_int_clear(lp->tmp);
 199         isl_int_clear(lp->tmp2);
 200         isl_vec_free(lp->row);
 201         free(lp->stack);
 202         isl_tab_free(lp->tab);
 203         isl_ctx_deref(lp->ctx);
 204         free(lp);
 205 }
 206
 207 static int add_lp_row(struct tab_lp *lp, isl_int *row, int dim)
 208 {
 209         lp->stack[lp->neq] = isl_tab_snap(lp->tab);
 210
 211         isl_int_set_si(lp->row->el[0], 0);
 212         isl_seq_cpy(lp->row->el + 1, row, lp->dim);
 213         isl_seq_neg(lp->row->el + 1 + lp->dim, row, lp->dim);
 214
 215         lp->tab = isl_tab_add_valid_eq(lp->tab, lp->row->el);
 216
 217         return lp->neq++;
 218 }
 219
 220 static void get_alpha(struct tab_lp* lp, int row, mpq_t *alpha)
 221 {
 222         row += lp->con_offset;
 223         isl_int_neg(mpq_numref(*alpha), lp->tab->dual->el[1 + row]);
 224         isl_int_set(mpq_denref(*alpha), lp->tab->dual->el[0]);
 225 }
 226
 227 static int del_lp_row(struct tab_lp *lp)
 228 {
 229         lp->neq--;
 230         return isl_tab_rollback(lp->tab, lp->stack[lp->neq]);
 231 }