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Changed initial guess of Newtons Square Root Method #19

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Changed initial guess of Newtons Square Root Method #19

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13 changes: 11 additions & 2 deletions include/real/real_math.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -201,8 +201,17 @@ namespace boost{
return literals::zero_exact<T>;
}

// initial guess
exact_number<T> result(x.digits, (x.exponent + 1)/2, true);
// initial guess using scalar estimate
exact_number<T> result;
if(x.exponent%2==0)
{
if(x.digits[0]>=1)
result=exact_number<T> (std::vector<T> {6}, (x.exponent)/2, true);
else
result=exact_number<T> (std::vector<T> {2}, (x.exponent)/2, true);
}
else
result=exact_number<T>(std::vector<T> {2}, (x.exponent-1)/2, true);

exact_number<T> error;
exact_number<T> max_error(std::vector<T> {1}, -max_error_exponent, true);
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