Re: [julia-users] display precision

2015-11-15 Thread David P. Sanders 


El domingo, 15 de noviembre de 2015, 12:45:11 (UTC-6), Yichao Yu escribió:
>
> On Sun, Nov 15, 2015 at 1:25 PM, digxx > 
> wrote: 
> > Is it possible to display the precision of a number to arbitrary 
> decimals 
> > points? 
> > For example if I want to display pi (or any other result) up to 1e6 
> > decimals?! 
>
>
Note that the BigFloat precision is given in binary digits, not decimal 
digits,
so you have to multiply the 10^6 that you want by log2(10) = 3.32...:

num_binary_digits = ceil(Int, 10^6 * log2(10))
set_bigfloat_precision(num_binary_digits)

@time s = string(big(pi))
length(s)

The results are 103 digits and

0.184317 seconds


Of course, actually *displaying* the string takes a lot longer (output is slow).

Re: [julia-users] display precision

2015-11-15 Thread Yichao Yu 
On Sun, Nov 15, 2015 at 1:25 PM, digxx  wrote:
> Is it possible to display the precision of a number to arbitrary decimals
> points?
> For example if I want to display pi (or any other result) up to 1e6
> decimals?!

For arbitrary result, you can't print arbitrary precision if your
calculation does not have that precision (unless you just want to see
1e6 zeros printed). You want to perform the calculation on BigFloat[1]
if you need that precision (and then printing it out should give you
the expected number of digits).

In theory, there could be a way to print out pi to a high precision
without converting it to a BigFloat first although I also don't see
why that's a useful thing to do in general.

[1] 
http://julia.readthedocs.org/en/latest/manual/integers-and-floating-point-numbers/#arbitrary-precision-arithmetic

[julia-users] display precision

2015-11-15 Thread digxx 
Is it possible to display the precision of a number to arbitrary decimals 
points?
For example if I want to display pi (or any other result) up to 1e6 
decimals?!