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Python OverflowError for Newton-Raphson root finding method

x=float(raw_input('Enter a number to show its square root'))
precise = 0.01
g=x/2.0
while abs(g**2-x)>=precise:
   g=g-(g**2-x)/2*g
print g

This is a python code based on Newton-Raphson Root Finding method. When I run this in Canopy, I can find root of 1. But when i input 25 to find the root, it says OverflowError: (34, 'Result too large') pointing out to the while abs(g**2-x)>=precise: line. Help appreciated

Solution

  • Are you sure about your algorithm. Move your print g inside your while loop and you will see that g is getting really really big, really fast. Then you are trying to square it. Is your denominator supposed to be 2*g? If so then you should put parenthesis around it like (2*g), because you are dividing by 2 and then multiplying by g. Probably not what you wanted to do.