Does this help?
jwith_bigfloat_precision(512) do
exp(BigFloat(1))
end
2.71828182845904523536028747135266249775724709369995957496696762772407663035354759457138217852516642742746639193200305992181741359662904357290033429526059559e+00
with 512 bits of precision
On Sunday, 11 January 2015 14:16:53 UTC, Hans W Borchers wrote:
>
> The following function computes Euler's constant e = exp(1.0) to n
> digits *exactly* (returning it as string):
>
> function dropletE(n::Int)
> a = fill(1, n+2)
> E = "2."
> for i in 1:n
> a = 10 * a
> for j in (n+2):-1:2
> a[j-1] = a[j-1] + div(a[j], j+1)
> a[j] = mod(a[j], j+1)
> end
> E = E * string(div(a[1], 2))
> a[1] = mod(a[1], 2)
> end
> return E
> end
>
> Comparing it with e calculated in Julia with the Big number class shows
> that the computation in Julia is only correct up to the 76th digit (of 78
> digits shown).
>
> julia> dropletE(100)
> "2.71828182845904523536028747135266249775724709369995
> 95749669676277240766303535475945713821785251664274"
>
> julia> exp(big(1.0)) # or simply:
> big(e)
> 2.71828182845904523536028747135266249775724709369995
> 9574966967627724076630353555e+00 with 256 bits of precision
>
> This corresponds well to the fact that Julia is utilizing the MPFR library
> (?) "with 256 bits of precision" only.
>
> Question: How can I change this behavior and force Julia to apply more
> digits, e.g. 4096 bits, to get about 1200 correct decimal digits. Is there
> a parameter one can set, or do I need to recompile Julia with a certain
> option?
>
> [In R, with the MPFR package, one can set the number of digits with every
> single number defined as 'big', i.e. as MPFR number.]
>
