Counting Primes
TESTS:
sage: z = sage.functions.prime_pi.PrimePi()
sage: loads(dumps(z))
Function that counts the number of primes up to x
sage: loads(dumps(z)) == z
True
Bases: object
Return the number of primes \(\leq x\).
EXAMPLES:
sage: prime_pi(7)
4
sage: prime_pi(100)
25
sage: prime_pi(1000)
168
sage: prime_pi(100000)
9592
sage: prime_pi(0.5)
0
sage: prime_pi(-10)
0
sage: prime_pi(500509)
41581
The following test is to verify that ticket #4670 has been essentially resolved:
sage: prime_pi(10**10)
455052511
The prime_pi function allows for use of additional memory:
sage: prime_pi(500509, 8)
41581
The prime_pi function also has a special plotting method, so it plots quickly and perfectly as a step function:
sage: P = plot(prime_pi, 50,100)
Draw a plot of the prime counting function from xmin to xmax. All additional arguments are passed on to the line command.
WARNING: we draw the plot of prime_pi as a stairstep function with explicitly drawn vertical lines where the function jumps. Technically there should not be any vertical lines, but they make the graph look much better, so we include them. Use the option vertical_lines=False to turn these off.
EXAMPLES:
sage: plot(prime_pi, 1, 100)
sage: prime_pi.plot(-2,50,thickness=2, vertical_lines=False)