Repunit primes: Difference between revisions
Added C++ solution
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=={{header|C++}}==
{{libheader|GMP}}
{{libheader|Primesieve}}
<lang cpp>#include <future>
#include <iomanip>
#include <iostream>
#include <vector>
#include <gmpxx.h>
#include <primesieve.hpp>
std::vector<uint64_t> repunit_primes(uint32_t base, uint64_t limit,
const std::vector<uint64_t>& primes) {
std::vector<uint64_t> result;
for (uint64_t prime : primes) {
mpz_class repunit(std::string(prime, '1'), base);
if (mpz_probab_prime_p(repunit.get_mpz_t(), 25) != 0)
result.push_back(prime);
}
return result;
}
int main() {
std::vector<uint64_t> primes;
const uint64_t limit = 2700;
primesieve::generate_primes(limit, &primes);
std::vector<std::future<std::vector<uint64_t>>> futures;
for (uint32_t base = 2; base <= 36; ++base) {
futures.push_back(std::async(
[base, &primes] { return repunit_primes(base, limit, primes); }));
}
std::cout << "Repunit prime digits (up to " << limit << ") in:\n";
for (uint32_t base = 2, i = 0; base <= 36; ++base, ++i) {
std::cout << "Base " << std::setw(2) << base << ':';
for (auto digits : futures[i].get())
std::cout << ' ' << digits;
std::cout << '\n';
}
}</lang>
{{out}}
This takes about 4 minutes 24 seconds (3.2GHz Quad-Core Intel Core i5).
<pre>
Repunit prime digits (up to 2700) in:
Base 2: 2 3 5 7 13 17 19 31 61 89 107 127 521 607 1279 2203 2281
Base 3: 3 7 13 71 103 541 1091 1367 1627
Base 4: 2
Base 5: 3 7 11 13 47 127 149 181 619 929
Base 6: 2 3 7 29 71 127 271 509 1049
Base 7: 5 13 131 149 1699
Base 8: 3
Base 9:
Base 10: 2 19 23 317 1031
Base 11: 17 19 73 139 907 1907 2029
Base 12: 2 3 5 19 97 109 317 353 701
Base 13: 5 7 137 283 883 991 1021 1193
Base 14: 3 7 19 31 41 2687
Base 15: 3 43 73 487 2579
Base 16: 2
Base 17: 3 5 7 11 47 71 419
Base 18: 2
Base 19: 19 31 47 59 61 107 337 1061
Base 20: 3 11 17 1487
Base 21: 3 11 17 43 271
Base 22: 2 5 79 101 359 857
Base 23: 5
Base 24: 3 5 19 53 71 653 661
Base 25:
Base 26: 7 43 347
Base 27: 3
Base 28: 2 5 17 457 1423
Base 29: 5 151
Base 30: 2 5 11 163 569 1789
Base 31: 7 17 31
Base 32:
Base 33: 3 197
Base 34: 13 1493
Base 35: 313 1297
Base 36: 2
</pre>
=={{header|F_Sharp|F#}}==
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