Created
January 17, 2015 22:28
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A prime generator algorithm, it is buggy because beyond starting point 2 nothing is handled and it hangs in range 2 to 1billion
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| def getprimes(start=2, upto=100): | |
| """ | |
| Generate primes between a given range defined by | |
| :start: and :upto: vars. | |
| """ | |
| #NOTE: np.arrange is faster then python for loop | |
| primes = np.arange(2, upto+1) | |
| isprime = np.ones(upto-1, dtype=bool) | |
| #find the first prime before starting this loop to optimize | |
| for factor in primes[:int(upto**0.5)]: | |
| if isprime[factor-2]: isprime[factor*2-2::factor]=0 | |
| start = start - 2 if start > 2 else start -1 | |
| return primes[isprime][start:upto] |
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http://rebrained.com/?p=458