diff options
Diffstat (limited to 'games/primes/primes.c')
| -rw-r--r-- | games/primes/primes.c | 42 |
1 files changed, 13 insertions, 29 deletions
diff --git a/games/primes/primes.c b/games/primes/primes.c index cf23fef..08141b6 100644 --- a/games/primes/primes.c +++ b/games/primes/primes.c @@ -56,7 +56,7 @@ static const char rcsid[] = * chongo <for a good prime call: 391581 * 2^216193 - 1> /\oo/\ * * usage: - * primes [start [stop]] + * primes [-h] [start [stop]] * * Print primes >= start and < stop. If stop is omitted, * the value 4294967295 (2^32-1) is assumed. If start is @@ -88,23 +88,6 @@ static const char rcsid[] = */ static char table[TABSIZE]; /* Eratosthenes sieve of odd numbers */ -/* - * prime[i] is the (i-1)th prime. - * - * We are able to sieve 2^32-1 because this byte table yields all primes - * up to 65537 and 65537^2 > 2^32-1. - */ -extern ubig prime[]; -extern ubig *pr_limit; /* largest prime in the prime array */ - -/* - * To avoid excessive sieves for small factors, we use the table below to - * setup our sieve blocks. Each element represents a odd number starting - * with 1. All non-zero elements are factors of 3, 5, 7, 11 and 13. - */ -extern char pattern[]; -extern size_t pattern_size; /* length of pattern array */ - static int hflag; static void primes(ubig, ubig); @@ -193,7 +176,7 @@ static ubig read_num_buf(void) { ubig val; - char *p, buf[100]; /* > max number of digits. */ + char *p, buf[LINE_MAX]; /* > max number of digits. */ for (;;) { if (fgets(buf, sizeof(buf), stdin) == NULL) { @@ -225,8 +208,9 @@ primes(ubig start, ubig stop) char *q; /* sieve spot */ ubig factor; /* index and factor */ char *tab_lim; /* the limit to sieve on the table */ - ubig *p; /* prime table pointer */ + const ubig *p; /* prime table pointer */ ubig fact_lim; /* highest prime for current block */ + ubig mod; /* temp storage for mod */ /* * A number of systems can not convert double values into unsigned @@ -296,28 +280,28 @@ primes(ubig start, ubig stop) /* note highest useful factor and sieve spot */ if (stop-start > TABSIZE+TABSIZE) { tab_lim = &table[TABSIZE]; /* sieve it all */ - fact_lim = (int)sqrt( - (double)(start)+TABSIZE+TABSIZE+1.0); + fact_lim = sqrt(start+1.0+TABSIZE+TABSIZE); } else { tab_lim = &table[(stop-start)/2]; /* partial sieve */ - fact_lim = (int)sqrt((double)(stop)+1.0); + fact_lim = sqrt(stop+1.0); } /* sieve for factors >= 17 */ factor = 17; /* 17 is first prime to use */ p = &prime[7]; /* 19 is next prime, pi(19)=7 */ do { /* determine the factor's initial sieve point */ - q = (char *)(start%factor); /* temp storage for mod */ - if ((long)q & 0x1) { - q = &table[(factor-(long)q)/2]; + mod = start%factor; + if (mod & 0x1) { + q = &table[(factor-mod)/2]; } else { - q = &table[q ? factor-((long)q/2) : 0]; + q = &table[mod ? factor-(mod/2) : 0]; } /* sive for our current factor */ for ( ; q < tab_lim; q += factor) { *q = '\0'; /* sieve out a spot */ } - } while ((factor=(ubig)(*(p++))) <= fact_lim); + factor = *p++; + } while (factor <= fact_lim); /* * print generated primes @@ -333,6 +317,6 @@ primes(ubig start, ubig stop) static void usage(void) { - (void)fprintf(stderr, "usage: primes [-h] [start [stop]]\n"); + fprintf(stderr, "usage: primes [-h] [start [stop]]\n"); exit(1); } |
