files / problems / c7-shannon / compute / q3 / search_hamming13.c
/* Hamming distance 13 around the 367-set (6-out / 7-in), high-blocker cases.
q2 finished odd Hamming distance 11. The 6-blocker vertices determine
the removal 6-set (case A). A 5-blocker vertex plus one extra removal
is case B. Cases that add only ≤4-blocker vertices are left to SAT
or later work.
gcc -O3 -o q3/search_hamming13 q3/search_hamming13.c
./q3/search_hamming13 R367.txt
*/
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#define NV 16807
#define DIM 5
#define SEEDN 367
static int coord[NV][DIM];
static int neigh[NV][243];
static int seed[SEEDN];
static int in_seed[NV];
static int nblock[NV];
static int block_list[NV][16];
static int n_by_nb[16];
static int *by_nb[16];
static int encode_coords(const int c[DIM]) {
int v = 0;
for (int i = 0; i < DIM; i++) v = v * 7 + c[i];
return v;
}
static void fill_tables(void) {
for (int v = 0; v < NV; v++) {
int x = v;
for (int i = DIM - 1; i >= 0; i--) {
coord[v][i] = x % 7;
x /= 7;
}
int n = 0;
int o0, o1, o2, o3, o4;
for (o0 = -1; o0 <= 1; o0++)
for (o1 = -1; o1 <= 1; o1++)
for (o2 = -1; o2 <= 1; o2++)
for (o3 = -1; o3 <= 1; o3++)
for (o4 = -1; o4 <= 1; o4++) {
int c[DIM];
c[0] = (coord[v][0] + o0 + 7) % 7;
c[1] = (coord[v][1] + o1 + 7) % 7;
c[2] = (coord[v][2] + o2 + 7) % 7;
c[3] = (coord[v][3] + o3 + 7) % 7;
c[4] = (coord[v][4] + o4 + 7) % 7;
neigh[v][n++] = encode_coords(c);
}
}
}
static int load_seed(const char *path) {
FILE *f = fopen(path, "r");
if (!f) return -1;
int n = 0;
char line[256];
while (fgets(line, sizeof line, f)) {
int c[5];
char *p = line;
while (*p == ' ' || *p == '\t') p++;
if (*p == '#' || *p == '\0' || *p == '\n') continue;
if (p[0] >= '0' && p[0] <= '6' && p[1] >= '0' && p[1] <= '6') {
for (int i = 0; i < 5; i++) c[i] = p[i] - '0';
} else {
for (int i = 0; i < 5; i++) {
int x, cons = 0;
if (sscanf(p, "%d%n", &x, &cons) != 1) {
fclose(f);
return -1;
}
c[i] = x;
p += cons;
}
}
seed[n++] = encode_coords(c);
}
fclose(f);
return n;
}
static int adj_uv(int u, int v) {
if (u == v) return 0;
for (int i = 0; i < 5; i++) {
int d = coord[u][i] - coord[v][i];
if (d < 0) d = -d;
if (d > 3) d = 7 - d;
if (d > 1) return 0;
}
return 1;
}
static int exact_mis(const int *verts, int n) {
if (n <= 0) return 0;
if (n > 64) {
int take = 0;
uint8_t used[512];
memset(used, 0, (size_t)n);
for (int i = 0; i < n; i++) {
if (used[i]) continue;
take++;
for (int j = i + 1; j < n; j++)
if (!used[j] && adj_uv(verts[i], verts[j])) used[j] = 1;
used[i] = 1;
}
return take;
}
uint64_t neighm[64];
memset(neighm, 0, sizeof neighm);
for (int i = 0; i < n; i++)
for (int j = i + 1; j < n; j++)
if (adj_uv(verts[i], verts[j])) {
neighm[i] |= 1ull << j;
neighm[j] |= 1ull << i;
}
int best = 0;
int nodes = 0;
uint64_t full = (n == 64) ? ~0ull : ((1ull << n) - 1);
void rec(uint64_t cand, int sofar) {
if (++nodes > 400000) return;
if (sofar + __builtin_popcountll(cand) <= best) return;
if (cand == 0) {
if (sofar > best) best = sofar;
return;
}
int v = __builtin_ctzll(cand);
rec(cand & ~neighm[v] & ~(1ull << v), sofar + 1);
rec(cand & ~(1ull << v), sofar);
}
rec(full, 0);
return best;
}
static int subset_of(int v, const uint8_t *inR) {
for (int i = 0; i < nblock[v]; i++)
if (!inR[block_list[v][i]]) return 0;
return 1;
}
static void collect_freed(const uint8_t *inR, int *out, int *n) {
int m = 0;
for (int nb = 1; nb <= 6; nb++) {
for (int t = 0; t < n_by_nb[nb]; t++) {
int v = by_nb[nb][t];
if (subset_of(v, inR)) out[m++] = v;
}
}
*n = m;
}
int main(int argc, char **argv) {
const char *path = argc > 1 ? argv[1] : "R367.txt";
clock_t t0 = clock();
fill_tables();
int n0 = load_seed(path);
if (n0 != SEEDN) {
fprintf(stderr, "bad seed n=%d\n", n0);
return 1;
}
memset(in_seed, 0, sizeof in_seed);
for (int i = 0; i < SEEDN; i++) in_seed[seed[i]] = 1;
memset(nblock, 0, sizeof nblock);
for (int i = 0; i < SEEDN; i++) {
for (int k = 0; k < 243; k++) {
int u = neigh[seed[i]][k];
if (in_seed[u]) continue;
if (nblock[u] < 16) block_list[u][nblock[u]++] = i;
}
}
memset(n_by_nb, 0, sizeof n_by_nb);
for (int v = 0; v < NV; v++) {
if (in_seed[v]) continue;
int nb = nblock[v];
if (nb >= 0 && nb < 16) n_by_nb[nb]++;
}
printf("blocker_hist");
for (int nb = 0; nb < 16; nb++) printf(" %d:%d", nb, n_by_nb[nb]);
printf("\n");
for (int nb = 0; nb < 16; nb++) {
by_nb[nb] = malloc(sizeof(int) * (n_by_nb[nb] + 1));
n_by_nb[nb] = 0;
}
for (int v = 0; v < NV; v++) {
if (in_seed[v]) continue;
int nb = nblock[v];
if (nb >= 0 && nb < 16) by_nb[nb][n_by_nb[nb]++] = v;
}
int best_mis = 0, best_freed = 0, nA = 0, hit = 0;
int freed[8192];
for (int t = 0; t < n_by_nb[6]; t++) {
int v = by_nb[6][t];
uint8_t inR[SEEDN];
memset(inR, 0, sizeof inR);
for (int i = 0; i < nblock[v]; i++) inR[block_list[v][i]] = 1;
int nf = 0;
collect_freed(inR, freed, &nf);
int a = exact_mis(freed, nf);
if (a > best_mis) best_mis = a;
if (nf > best_freed) best_freed = nf;
nA++;
if (a >= 7) {
printf("CASE_A HIT v=%d freed=%d alpha=%d\n", v, nf, a);
hit = 1;
break;
}
}
printf("caseA n=%d best_mis=%d max_freed=%d t=%.2fs\n", nA, best_mis,
best_freed, (double)(clock() - t0) / CLOCKS_PER_SEC);
fflush(stdout);
int best_mis_B = 0, max_freed_B = 0, nB = 0;
if (!hit) {
int base_freed[8192];
for (int t = 0; t < n_by_nb[5]; t++) {
int v = by_nb[5][t];
uint8_t baseR[SEEDN];
memset(baseR, 0, sizeof baseR);
for (int i = 0; i < nblock[v]; i++) baseR[block_list[v][i]] = 1;
int nbase = 0;
collect_freed(baseR, base_freed, &nbase);
for (int e = 0; e < SEEDN; e++) {
if (baseR[e]) continue;
int nf = nbase;
memcpy(freed, base_freed, (size_t)nbase * sizeof(int));
for (int k = 0; k < 243; k++) {
int u = neigh[seed[e]][k];
if (in_seed[u]) continue;
if (nblock[u] > 6) continue;
int ok = 1, uses_e = 0;
for (int i = 0; i < nblock[u]; i++) {
int b = block_list[u][i];
if (b == e) uses_e = 1;
else if (!baseR[b]) {
ok = 0;
break;
}
}
if (ok && uses_e) {
if (nf < 8192) freed[nf++] = u;
}
}
int a = exact_mis(freed, nf);
if (a > best_mis_B) best_mis_B = a;
if (nf > max_freed_B) max_freed_B = nf;
nB++;
if (a >= 7) {
printf("CASE_B HIT v=%d extra=%d freed=%d alpha=%d\n", v, e, nf,
a);
hit = 1;
goto done;
}
}
if ((t + 1) % 400 == 0) {
printf(" caseB %d/%d best_mis=%d max_freed=%d t=%.1fs\n", t + 1,
n_by_nb[5], best_mis_B, max_freed_B,
(double)(clock() - t0) / CLOCKS_PER_SEC);
fflush(stdout);
}
}
}
done:
printf("caseB n=%d best_mis=%d max_freed=%d\n", nB, best_mis_B, max_freed_B);
printf("DONE hit=%d caseA_best=%d caseB_best=%d t=%.2fs\n", hit, best_mis,
best_mis_B, (double)(clock() - t0) / CLOCKS_PER_SEC);
if (!hit)
printf("no 368 in Hamming-13 cases A+B (added vertex with 5 or 6 "
"blockers)\n");
return 0;
}