static void Sqrt(BigNumber src, BigNumber dst, int places)
{
int ii, nexp, tolerance, dplaces;
bool bflag;
if (src.signum <= 0)
{
if (src.signum == -1)
{
throw new BigNumberException("'Sqrt',Invalid Argument");
}
}
BigNumber last_x = new BigNumber();
BigNumber guess = new BigNumber();
BigNumber tmpN = new BigNumber();
BigNumber tmp7 = new BigNumber();
BigNumber tmp8 = new BigNumber();
BigNumber tmp9 = new BigNumber();
BigNumber.Copy(src, tmpN);
nexp = src.exponent / 2;
tmpN.exponent -= 2 * nexp;
BigNumber.SQrtGuess(tmpN, guess);
tolerance = places + 4;
dplaces = places + 16;
bflag = false;
BigNumber.Neg(BigNumber.Ten, last_x);
ii = 0;
while (true)
{
BigNumber.Mul(tmpN, guess, tmp9);
BigNumber.Mul(tmp9, guess, tmp8);
BigNumber.Round(tmp8, tmp7, dplaces);
BigNumber.Sub(BigNumber.Three, tmp7, tmp9);
BigNumber.Mul(tmp9, guess, tmp8);
BigNumber.Mul(tmp8, BigNumber.BN_OneHalf, tmp9);
if (bflag)
{
break;
}
BigNumber.Round(tmp9, guess, dplaces);
if (ii != 0)
{
BigNumber.Sub(guess, last_x, tmp7);
if (tmp7.signum == 0)
{
break;
}
/*
* if we are within a factor of 4 on the error term,
* we will be accurate enough after the *next* iteration
* is complete. (note that the sign of the exponent on
* the error term will be a negative number).
*/
if ((-4 * tmp7.exponent) > tolerance)
{
bflag = true;
}
}
BigNumber.Copy(guess, last_x);
ii++;
}
BigNumber.Mul(tmp9, tmpN, tmp8);
BigNumber.Round(tmp8, dst, places);
dst.exponent += nexp;
}
