On Tue, 2008-07-29 at 01:12 +0200, [EMAIL PROTECTED] wrote:
> Message: 3
> Date: Mon, 28 Jul 2008 13:26:13 -0500
> From: "Daniel Sarmiento" <[EMAIL PROTECTED]>
> Subject: Re: [Tutor] Memory error - how to manage large data sets?
> To: tutor@python.org
> Message-ID:
> <[EMAIL PROTECTED]>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hi
>
> I tried to run your code and checked (with top) the memory ussage and
> it uses more than 2 Gb of memory.
>
> I tried to modify the code a little bit to use less memory and came up
> with this:
>
> fib = {0:0,1:1}
> even = []
>
> def fibonacci(x,y):
> return x+y
>
> for j in xrange (2,1000000):
> i = fib[j-1] + fib[j-2]
> if i % 2 == 0:
> even.append(i)
> fib = {j-1:fib[j-1], j:i}
>
> total = reduce(fibonacci,even)
> print total
>
> First, I replaced range with xrange.
> I figured that you only need the last two values in the fibonnaci
> series to calculate the next value, so I replaced the fib list with a
> dictionary to only store the last two values instead of the whole
> series.
>
> It looks like the progam still hangs and I did not notice any memory
> imrovements when running it with 1 000 000
>
> Am I wrong thinking that the modifications I made help use less
> memory?
>
I have realised that when you need to work with large numbers, lists are
slow and tend to gobble up bytes. Another thing try to be as simple as
possible :). This is how I would approach the problem, without using
lists. It produces the result instantly, even for large numbers like a
100, 000, 000.
def fibonacci()
a = 0
b = 1
evenTotal = 0
while a < 100000000:
a,b = b,a+b
if a%2 == 0:
evenTotal += a
print evenTotal
Does this help?
Kinuthia...
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