Download or view NewtonDivision.frink in plain text format
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.
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Alan Eliasen was born 20139 days, 6 hours, 21 minutes ago.