# Project Euler 187
# Count semiprimes n < 10^8.
extern {
function calloc(n: i64, size: i64) -> ptr<void>
function free(p: ptr<void>) -> void
}
function main() -> i32 {
let LIMIT: i64 = 100000000
let N: i64 = LIMIT / 2
let sieve: ptr<i8> = calloc(N + 1, 1)
if sieve == null { return 1 }
let mut i: i64 = 0
while i <= N {
sieve[i] = 1
i = i + 1
}
sieve[0] = 0
sieve[1] = 0
let mut p: i64 = 2
while p * p <= N {
if sieve[p] == 1 {
let mut m: i64 = p * p
while m <= N {
sieve[m] = 0
m = m + p
}
}
p = p + 1
}
# count primes and collect
let mut pc: i64 = 0
i = 2
while i <= N {
if sieve[i] == 1 { pc = pc + 1 }
i = i + 1
}
let primes: ptr<i64> = calloc(pc, 8)
if primes == null { free(sieve); return 1 }
let mut idx: i64 = 0
i = 2
while i <= N {
if sieve[i] == 1 {
primes[idx] = i
idx = idx + 1
}
i = i + 1
}
let mut count: i64 = 0
let mut j: i64 = pc - 1
let mut ii: i64 = 0
while ii < pc {
let pp: i64 = primes[ii]
if pp * pp >= LIMIT { break }
while j >= ii && primes[j] * pp >= LIMIT {
j = j - 1
}
if j < ii { break }
count = count + (j - ii + 1)
ii = ii + 1
}
printf("%lld\n", count)
free(primes)
free(sieve)
return 0
}
Generated C
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
/* Flow runtime helpers */
typedef struct flow_temp_node { struct flow_temp_node* next; } flow_temp_node;
static flow_temp_node* flow_temp_head = NULL;
static int flow_temp_atexit_set = 0;
__attribute__((unused)) static void flow_temp_free_all(void) {
while (flow_temp_head) {
flow_temp_node* n = flow_temp_head;
flow_temp_head = n->next;
free(n);
}
}
__attribute__((unused)) static void* flow_temp_alloc(size_t nbytes) {
flow_temp_node* node = (flow_temp_node*)malloc(sizeof(flow_temp_node) + nbytes);
if (!node) return NULL;
node->next = flow_temp_head;
flow_temp_head = node;
if (!flow_temp_atexit_set) {
flow_temp_atexit_set = 1;
atexit(flow_temp_free_all);
}
return (void*)(node + 1);
}
#ifndef FLOW_DIAG
#define FLOW_DIAG(msg) fprintf(stderr, "%s", (msg))
#endif
#ifndef FLOW_LOG
#define FLOW_LOG(fmt, ...) printf(fmt, __VA_ARGS__)
#endif
#ifndef FLOW_LOG_EMPTY
#define FLOW_LOG_EMPTY(fmt) printf(fmt)
#endif
static char* flow_strcat(const char* a, const char* b) {
size_t la = strlen(a ? a : ""), lb = strlen(b ? b : "");
char* r = (char*)flow_temp_alloc(la + lb + 1);
if (!r) return NULL;
if (la) memcpy(r, a, la);
if (lb) memcpy(r + la, b, lb);
r[la + lb] = '\0';
return r;
}
#define __flow_in_arr(arr, val) __extension__ ({ \
int _found = 0; \
size_t _n = sizeof(arr)/sizeof((arr)[0]); \
for (size_t _i = 0; _i < _n; _i++) { \
if ((arr)[_i] == (val)) { _found = 1; break; } \
} _found; })
/* Unified fault handler (MISRA #279) — override with -DFLOW_FAULT_HANDLER=fn */
#ifndef FLOW_FAULT_HANDLER
__attribute__((unused)) static inline void flow_fault_handler(const char* msg) {
fprintf(stderr, "flow: %s\n", msg ? msg : "fault");
abort();
#if defined(__GNUC__) || defined(__clang__)
__builtin_unreachable();
#endif
}
#else
#define flow_fault_handler FLOW_FAULT_HANDLER
#endif
#define flow_div_by_zero_handler() flow_fault_handler("division by zero")
#define flow_shift_ub_handler() flow_fault_handler("invalid shift (amount out of range or left-shift of negative)")
#ifndef FLOW_CHECKED_DIV
#define FLOW_CHECKED_DIV(L, R) (((R) != 0) ? ((L) / (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_MOD
#define FLOW_CHECKED_MOD(L, R) (((R) != 0) ? ((L) % (R)) : (flow_div_by_zero_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHL
#define FLOW_CHECKED_SHL(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull)) && ((L) >= 0)) ? ((L) << (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#ifndef FLOW_CHECKED_SHR
#define FLOW_CHECKED_SHR(L, R) ((((R) >= 0) && ((unsigned long long)(R) < (sizeof(L) * 8ull))) ? ((L) >> (R)) : (flow_shift_ub_handler(), (L) * 0))
#endif
#include <math.h>
void* _ui_state = NULL;
static inline float i32_to_f32(int32_t v) { return (float)v; }
/* Host stub for @gpu kernels (device codegen replaces this). */
static inline int32_t gpu_thread_id(void) { return 0; }
int32_t main(void);
int32_t main(void) {
int64_t LIMIT = 100000000;
int64_t N = FLOW_CHECKED_DIV((LIMIT), (2));
int8_t* sieve = (int8_t*)(calloc((N + 1), 1));
if (sieve == NULL) {
return 1;
}
int64_t i = 0;
while (i <= N) {
sieve[i] = 1;
i = (i + 1);
}
sieve[0] = 0;
sieve[1] = 0;
int64_t p = 2;
while ((p * p) <= N) {
if (sieve[p] == 1) {
int64_t m = (p * p);
while (m <= N) {
sieve[m] = 0;
m = (m + p);
}
}
p = (p + 1);
}
int64_t pc = 0;
i = 2;
while (i <= N) {
if (sieve[i] == 1) {
pc = (pc + 1);
}
i = (i + 1);
}
int64_t* primes = (int64_t*)(calloc(pc, 8));
if (primes == NULL) {
free(sieve);
return 1;
}
int64_t idx = 0;
i = 2;
while (i <= N) {
if (sieve[i] == 1) {
primes[idx] = i;
idx = (idx + 1);
}
i = (i + 1);
}
int64_t count = 0;
int64_t j = (pc - 1);
int64_t ii = 0;
while (ii < pc) {
int64_t pp = primes[ii];
if ((pp * pp) >= LIMIT) {
break;
}
while ((j >= ii && (primes[j] * pp) >= LIMIT)) {
j = (j - 1);
}
if (j < ii) {
break;
}
count = (count + ((j - ii) + 1));
ii = (ii + 1);
}
printf("%lld\n", count);
free(primes);
free(sieve);
return 0;
}