Question

for ps1b: http://dpaste.com/564911/
i tried to just use the program i made for ps1a with modifications, but i'm kind of stuck. can someone point me in the right direction? :)

Answer 1

I think the problem may be line 25. Are you sure you want to add log(2) each time? Shouldn't it be the log(current prime number)?

Answer 2

the code was executing the same even without line 25, which was added later because i realized i needed to include log(2) in my sum. i don't see how it would be executing each time anyways as it's outside my loop.

Answer 3

Which is correct: I don't see the need for the log(2) line anyway. I believe it should be covered in the previous line when you wrote prime_c = prime_c + 2.

I think it's because you didn't actually start at 2 for your first prime. You said that this was your modification to your answer for ps1a. Lots of people finds it convenient (me included) to skip 2, 3 and even 5 for that prime number problem. And rightly so. But modifying this for the second problem would be troublesome because of the skipped primes. See for example your initial divider. 2 can't possibly be divided be 3, couldn't it?

Answer 4

Wait a minute. Did you actually test your solution for ps1a? Did it work correctly?

Answer 5

Yes that does work correctly. I think I know what the problem is now. Thanks everyone for your help!

Answer 6

well the problem is your code includes 1 as a prime number...the logarithm sum is absolutely correct...and the second thing is u need to get the ratio of log sums and the last prime number...
that shud be nearly 1 :)
for proof..check these codes out..the first one is a modified version of ur code..
and the second is mine
http://dpaste.com/hold/565013/
http://dpaste.com/hold/565016/

Answer 7

@ Lifeburner ..his code actually includes 3,5 and 7 :)

Answer 8

The problem is asking for the sum of the logs of all the primes less than n. NOT the sum of the logs of the first n primes.

So for n = 10 the primes would be: 2,3,5,7.
NOT 2,3,5,7,11,13,17,19,23,29

Answer 9

yea n everybody seems to get the problem wrong..but my code above is computing sum of the logs of all the primes less than n :)

Answer 10

ya, my answer was pretty bad:( just kind of glanced at your code first thing this morning while half asleep...

Answer 11

I just woke up..and i am still half asleep.. ;)
there is no place like bed...[yawn]

Answer 12

Sunu, I'm not sure I get your answer. In line 10 you say "while x > y:". But x will always be equal to y since you already gave them values in the first few lines and they haven't changed.

Answer 13

For that there is a x=x+2 in line 18..
sorry actually i have been too lazy to comment in my codes...from now on i'll try to comment..:(

Answer 14

bwCA, i caught that. stupid mistake on my part. it's running fine now :)