How can I avoid infinite while loop?

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Shashanka 2014-7-11

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评论： Shashanka 2014-7-11

N = 1; while (N<11) n = ((N*2)+(N+1))/N; N = n end

I wish to assign the value of 'n' to 'N' and compare if it's less than '11' and again enter the loop until 'N' is equal to 11. Please help.

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Answer 1

dpb 2014-7-11

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Well, since

 ((N*2)+(N+1))/N = (2*N+N+1)/N = (3*N+1)/N
n=3+1/N

and the expression approaches 3+ as a limit, never approaching anything near 11, the answer to the question posed is "you can't".

Need a different problem statement; perhaps you're looking for the point at which the change is less than some epsilon or something of that nature?

I'll wait for clarification of the actual problem nature before guessing further...

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Shashanka 2014-7-11

Thank you for the response! The example was a simplified version of the code I'm trying to run, which has decimal inputs. I have attached an image of the actual code below for your reference. The 'AxIFN' is to be updated with the latest value of 'AxIFN1' which is calculated with each iteration. Finally giving a value of 'AxIFN' which is less than '0.4'.

Thank you!

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Answer 2

Daniel 2014-7-11

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Set a number equal to the number of times you want to loop (this case I chose 11), subtract each time you're in the loop, and add an and condition

LOOP_LIMIT = 11;
N = 1;
while (N < 11 && LOOP_LIMIT > 0)
    n = ((N*2)+(N+1))/N;
    N = n;
    LOOP_LIMIT = LOOP_LIMIT-1;
end

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Shashanka 2014-7-11

Thank you for the response! The example was a simplified version of the code I'm trying to run, which has decimal inputs. I have attached an image of the actual code below for your reference. The 'AxIFN' is to be updated with the latest value of 'AxIFN1' which is calculated with each iteration. Finally giving a value of 'AxIFN' which is less than '0.4'.

Thank you!

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Answer 3

C.J. Harris 2014-7-11

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编辑：C.J. Harris 2014-7-11

You have an infinity loop because your seed (N) is starting at one. Note that your equation ((N*2)+(N+1))/N is in fact equal to 3+(1/N), thereby meaning you'll only get 11 (or greater) for values less than 0.125.

Not sure why you even need a loop, can't you just rearrange, therefore getting n = 1/(11-3) = 0.125.

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Shashanka 2014-7-11

Thank you for the response! The example was a simplified version of the code I'm trying to run, which has decimal inputs. I have attached an image of the actual code below for your reference. The 'AxIFN' is to be updated with the latest value of 'AxIFN1' which is calculated with each iteration. Finally giving a value of 'AxIFN' which is less than '0.4'.

Thank you!

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