// Test Probable Cunningham Chain for: n
// fSophieGermain:
// true - Test for Cunningham Chain of first kind (n, 2n+1, 4n+3, ...)
// false - Test for Cunningham Chain of second kind (n, 2n-1, 4n-3, ...)
// Return value:
// true - Probable Cunningham Chain found (length at least 2)
// false - Not Cunningham Chain
static
bool CunnChainTest(mpz_t *n, bool fSophieGermain, bool fFermatTest, unsigned int *pnProbableChainLength)
{
*pnProbableChainLength = 0;
mpz_t N;
mpz_init_set(N, *n);
// Fermat test for n first
if (!PrimeTest(&N, pnProbableChainLength))
{
mpz_clear(N);
return false;
}
// Euler-Lagrange-Lifchitz test for the following numbers in chain
while (true)
{
TargetIncrementLength(pnProbableChainLength);
mpz_add(N, N, N);
if (fSophieGermain)
mpz_add_ui(N, N, 1);
else
mpz_sub_ui(N, N, 1);
//disabled, see SpecialPrimeTest() comments for further information
/*if (fFermatTest)
{
if (!PrimeTest(&N, pnProbableChainLength))
break;
}
else
{
if (!SpecialPrimeTest(&N, fSophieGermain, pnProbableChainLength))
break;
}*/
if (!PrimeTest(&N, pnProbableChainLength))
break;
}
mpz_clear(N);
#ifdef SUPERDEBUG
printf("PCCT => %u (%u)\n", TargetGetLength(*pnProbableChainLength), *pnProbableChainLength);
#endif
return (TargetGetLength(*pnProbableChainLength) >= 2);
}
// stP is inclusive and prime; endP is exclusive
static void* CalculationThread(void *context)
{
PCALC_THREAD_CONTEXT tcontext = (PCALC_THREAD_CONTEXT)context;
unsigned long P, setBits;
unsigned int primality;
char *primeStr;
setBits = 0;
for (;;)
{
// Reserve the next prime P value for us to test
P = GetNextPrimeP();
// Print a message to the terminal
PRINT_MSG(MSG_VERBOSE, "Thread %d: Testing P=%lu", tcontext->threadIndex, P);
// Only set bits that weren't set before
while (setBits < P)
{
mpz_setbit(tcontext->nextPrime, setBits);
setBits++;
}
// Check the result for primality
primality = mpz_probab_prime_p(tcontext->nextPrime, DIVISIONS_FOR_PRIMALITY);
switch (primality)
{
case GMP_DEF_COMPOSITE:
// Composite number is composite
break;
case GMP_PROB_PRIME:
// Probably prime, but we need to check for sure
if (PrimeTest(P, &tcontext->nextPrime) != GMP_DEF_PRIME)
{
// More extensive test showed it was composite
break;
}
// Else fall through to prime case
case GMP_DEF_PRIME:
// Definitely prime
primeStr = mpz_get_str(NULL, 10, tcontext->nextPrime);
if (primeStr)
{
PRINT_MSG(MSG_INFO, "Thread %d --- Mersenne prime found (P=%lu): %s",
tcontext->threadIndex, P, primeStr);
GmpFree(primeStr, strlen(primeStr)+1);
}
else
{
PRINT_MSG(MSG_WARNING, "Unable to allocate memory to output prime!");
}
break;
}
}
// Unreachable code
return NULL;
}
