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Better table algorithm for visited table implementing a very simple hashset

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This commit is contained in:
Claudio Maggioni 2019-12-11 10:15:29 +01:00
parent c0a0639105
commit f1a0bd9614
1 changed files with 69 additions and 10 deletions
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79
chess_paths/chess_paths.c
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@ -255,20 +255,79 @@ unsigned int decreasing_path_len(const struct chessboard* c,
return hops - 1;
}
void visit(bool* visited, unsigned columns, unsigned column, unsigned row) {
visited[column * columns + row] = true;
struct row_list {
unsigned row;
unsigned column;
struct row_list* next;
};
typedef struct row_list* visit_table;
unsigned long alloc = 0;
unsigned long table_total_size(const struct chessboard*);
unsigned long table_hash(const struct chessboard*, unsigned, unsigned);
inline unsigned long table_total_size(const struct chessboard* c) {
return 100;
}
bool visited(bool* visited, unsigned columns, unsigned column, unsigned row) {
return visited[column * columns + row];
inline unsigned long table_hash(const struct chessboard* c, unsigned col,
unsigned row) {
return (value_at(c, col, row) ^ 0xDEADBEEF) % table_total_size(c);
}
visit_table* table_new(const struct chessboard* c) {
unsigned long table_size = table_total_size(c);
alloc += sizeof(struct row_list*) * table_size;
return calloc(table_size, sizeof(struct row_list*));
}
void table_visit(const struct chessboard* c, visit_table* visited,
unsigned column, unsigned row) {
unsigned long hash = table_hash(c, column, row);
struct row_list* prev = hash[visited];
alloc += sizeof(struct row_list);
hash[visited] = malloc(sizeof(struct row_list));
assert(hash[visited] != NULL);
hash[visited]->row = row;
hash[visited]->column = column;
hash[visited]->next = prev;
}
bool table_visited(const struct chessboard* c, visit_table* visited,
unsigned column, unsigned row) {
unsigned long hash = table_hash(c, column, row);
for (struct row_list* i = hash[visited]; i != NULL; i = i->next) {
if (i->row == row && i->column == column) return true;
}
return false;
}
void table_destroy(const struct chessboard* c, visit_table* visited) {
unsigned long table_size = table_total_size(c);
for (unsigned e = 0; e < table_size; e++) {
for (struct row_list* i = e[visited], *j; i != NULL;) {
j = i->next;
free(i);
i = j;
}
}
printf("alloc = %lu\n", alloc);
alloc = 0;
free(visited);
}
unsigned int simple_path_len(const struct chessboard* c,
struct piece_position* p) {
const unsigned int CC = columns(c);
bool* v = calloc(rows(c) * CC, sizeof(unsigned));
visit(v, CC, p->column, p->row);
visit_table* v = table_new(c);
table_visit(c, v, p->column, p->row);
#if DEBUG
print_visited(c, v);
#endif
@ -287,7 +346,7 @@ unsigned int simple_path_len(const struct chessboard* c,
#endif
while(poss != NULL) {
if (!visited(v, CC, poss->column, poss->row)) {
if (!table_visited(c, v, poss->column, poss->row)) {
next_v = value_at(c, poss->column, poss->row);
if (!has_next || next_v > base_v) {
has_next = true;
@ -301,14 +360,14 @@ unsigned int simple_path_len(const struct chessboard* c,
free(del);
}
visit(v, CC, p->column, p->row);
table_visit(c, v, p->column, p->row);
#if DEBUG
print_visited(c, v);
#endif
hops++;
}
free(v);
table_destroy(c, v);
return hops - 1;
}