[Tutor] Advise...
Jacob S.
keridee at jayco.net
Wed Jan 26 05:54:02 CET 2005
Hi all.
Long time no see. (About five days, right?)
Anyway, I know the first thing that some of you are going to say is using
eval(). I don't want a whole
guilt trip on security risks and all that. I do not want to share the code
with anyone else while it's on my
computer, and I sure don't have anyone near me that knows python. I would be
surprised if more than 50
people in Portland, IN knew anything about python. So security is not a
problem. I guess what I'm
looking for is someone who knows the Reimann Sum better than I do and can
tell me whether I can do
something to make it more efficient. It's horribly slow with ten thousand
steps-- I don't know the notation
very well, but it loops the loop O(step*(maximum-minimum)) times, which is
horribly sucky.
In case anyone doesn't know, Reimann's sum is the computer's version of
the definite integral, the area
under a curve in a particular domain.
Basic input and output.
If a curve is a straight line, say y = x, the area under the line on an
interval can be found by geometric means.
However, if you use a parabola, or any other function, say y = 3*x**2,
What is the function? 3*x*x
What is the minimum? 2
What is the maximum? 5
117.000435
Which, considering that it is supposed to be exactly 117, It's darn good.
Unfortunately, it also takes about
10 seconds to do all that.
Any suggestions? Any advice? TIA
Jacob Schmidt
############################
from __future__ import division
import psyco
psyco.full()
fofx = raw_input("What is the function? ")
minimum = raw_input("What is the minimum? ")
maximum = raw_input("What is the maximum? ")
minimum = float(minimum)
maximum = float(maximum)
total = 0
step = 100000
x = minimum
while minimum <= x <= maximum:
area = eval(fofx)*1/step
total = total+area
x = x+1/step
print total
#############################
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