quiver.h

   1 /*
   2  * Copyright (c) 2016, S. Gilles <sgilles@math.umd.edu>
   3  *
   4  * Permission to use, copy, modify, and/or distribute this software
   5  * for any purpose with or without fee is hereby granted, provided
   6  * that the above copyright notice and this permission notice appear
   7  * in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
  10  * WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
  11  * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
  12  * AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
  13  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
  14  * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
  15  * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  16  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 /* A rational number */
  20 struct rational {
  21         /* Numerator */
  22         int_fast8_t p;
  23
  24         /* Denominator */
  25         uint_fast8_t q;
  26 };
  27
  28 /* The structure for a vertex */
  29 struct vertex {
  30         /* A textual identifier for this vertex */
  31         char *name;
  32
  33         /* Whether this vertex is `fat' or not. Expected to be 1, 2, or 3. */
  34         uint_fast8_t fatness;
  35
  36         /* Drawing data: coordinates in `internal coordinates */
  37         int x;
  38         int y;
  39 };
  40
  41 /* The cluster algebra structure */
  42 struct quiver {
  43         /* How many vertices there actually are in the quiver */
  44         size_t v_num;
  45
  46         /* How many vertices we have allocated memory for */
  47         size_t v_len;
  48
  49         /* Vertices */
  50         struct vertex *v;
  51
  52         /* Edges - e_{ij} (fatness included, so E^t is not necessarily -E) */
  53         struct rational *e;
  54
  55         /* For detecting if quiver_mutate() creates an edge too high */
  56         unsigned int edge_weight_threshold;
  57 };
  58
  59 /* Add an arrow of weight a/b from i -> j, affecting e(i,j) and e(j,i) */
  60 int
  61 quiver_add_to_edge(struct quiver *q, size_t i, size_t j, int_fast8_t a,
  62                    uint_fast8_t b, const char **out_errstr);
  63
  64 /* Add a vertex with a name and weight */
  65 int
  66 quiver_add_vertex(struct quiver *q, size_t *out_i, const char *name,
  67                   uint_fast16_t fatness, int x, int y, const char **out_errstr);
  68
  69 /* Increase or decrease the fatness of a vertex, readjusting edges as well */
  70 int
  71 quiver_adjust_fatness(struct quiver *q, size_t i, int_fast8_t fatness, const
  72                       char **out_errstr);
  73
  74 /* Delete a vertex (and all associated edges) */
  75 int
  76 quiver_delete_vertex(struct quiver *q, size_t i, const char **out_errstr);
  77
  78 /* Set threshold: if quiver_mutate() creates an edge above, warn_out is set */
  79 int
  80 quiver_set_warning_threshold(struct quiver *q, unsigned int warn_threshold,
  81                              char **out_errstr);
  82
  83 /* Mutate the quiver at vertex k, setting warn_out if threshold is broken */
  84 int
  85 quiver_mutate(struct quiver *q, size_t k, int *out_warn, const
  86               char **out_errstr);