Square Root of a number

This is a discussion on Square Root of a number within the C++ Programming forums, part of the General Programming Boards category; whereas teh mothod I suggested does find 0 < x < 1 for all positive real numbers....

  1. #31
    Malum in se abachler's Avatar
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    whereas teh mothod I suggested does find 0 < x < 1 for all positive real numbers.
    Until you can build a working general purpose reprogrammable computer out of basic components from radio shack, you are not fit to call yourself a programmer in my presence. This is cwhizard, signing off.

  2. #32

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    By the way, ((U - L)/2) is the same thing as (U + L) / 2.
    Or, better yet, (U + L) >> 1.

    EDIT:
    didn't realize they were doubles
    Last edited by rudyman; 07-30-2008 at 04:44 PM.

  3. #33
    The larch
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    Are you sure bitshifting works with doubles, though?
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  4. #34
    Malum in se abachler's Avatar
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    Quote Originally Posted by anon View Post
    Are you sure bitshifting works with doubles, though?
    It doesnt. well, at least not as a fast divide by 2^N.
    Until you can build a working general purpose reprogrammable computer out of basic components from radio shack, you are not fit to call yourself a programmer in my presence. This is cwhizard, signing off.

  5. #35
    Algorithm Dissector iMalc's Avatar
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    You're trying to calculate the square root by using the Newton-Raphson method by the looks of it. The problem is that you got the formula wrong. Go back and look it up again!
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

  6. #36
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by iMalc View Post
    You're trying to calculate the square root by using the Newton-Raphson method by the looks of it. The problem is that you got the formula wrong. Go back and look it up again!
    I think it's less Newton-Raphson and more binary search. (I guess "bisection" is the more proper term in this context.)

  7. #37
    Algorithm Dissector iMalc's Avatar
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    Heck I see; you're right. That's horrible!
    My homepage
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    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

  8. #38
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    If you want to get really fancy with square roots, here's a link describing how to calculate square roots by hand:

    http://www.geocities.com/cnowlen/Cat...Squareroot.htm

    I once implemented this in a class that does arithmetic on arbitrary length integers. Granted, it wasn't as efficient as the gmp implementation, but it's still cool to learn how to do.

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