NewtonDivision.frink

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NewtonInvert[n, digits=getPrecision[]] :=
{
   origPrec = getPrecision[]
   setPrecision[20]
   x = 1./n
   log2 = log[2]
   iters = ceil[ log[(digits+1)/(log[17]/log2)] / log2 ]
   goodDigits = 20
   err = x * 10^-(digits)
   println["err is $err"]
   do
   {
      prec = min[digits+2, 2 * goodDigits]
      setPrecision[prec]
      oldX = x
      x = x (2 - n x)
//      println["x is $x"]
//      setPrecision[5]
      diff = abs[x-oldX]
//      println["diff is $diff"]
      if (diff == 0.0)
         goodDigits = digits + 2
      else
         goodDigits = ceil[(-approxLog2[diff] + 4)/ 3.321928094]
      println["Iter $i, goodDigits is " + goodDigits /* + "x is $x"*/]
   } while (diff > err)
   println["bailing.  diff was $diff"]
   return x
}

/*
start = now[]
n = NewtonInvert[640320,100000]
end = now[]
println["Time for inversion: " + (end-start)]

start = now[]
println[n]
end = now[]
println["Time for formatting: " + (end-start)]
*/


Download or view NewtonDivision.frink in plain text format


This is a program written in the programming language Frink.
For more information, view the Frink Documentation or see More Sample Frink Programs.

Alan Eliasen was born 19972 days, 13 hours, 48 minutes ago.