The following problem with vpa (variable precision arithmetic) occurs only in octave-4.0.1 win10 32b version and not in the linux 64b version. As you can see, the number "1/3" is inaccurately represented when digits is greater than 16 (which happens to be roughly the native precision of a double, and perhaps that is not a coincidence).
I wanted to try this also in octave-4.0.2, but I had trouble installing the symbolic package (contains vpa function) .
Any thoughts on what is going on here?
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%this is in win10 64b with octave 4.0.1 32b for windows (not cygwin version, not 64b version)
>> pkg load symbolic
>> x=vpa(1/3,21)
OctSymPy v2.4.0: this is free software without warranty, see source.
Initializing communication with SymPy using a popen2() pipe.
Using winwrapy.bat workaround for bug #43036 (Octave <= 4.0.2, on Windows)
Some output from the Python subprocess (pid 968) might appear next.
OctSymPy: Communication established. SymPy v1.0.
Python 3.5.1 (v3.5.1:37a07cee5969, Dec 6 2015, 01:54:25) [MSC v.1900 64 bit (AM
D64)]
x = (sym) 0.333333333333333314830
>> x=vpa(1/3,19)
x = (sym) 0.3333333333333333148
>> x=vpa(1/3,30)
x = (sym) 0.333333333333333314829616256247
>> x=vpa(1/3,20)
x = (sym) 0.33333333333333331483
>> x=vpa(1/3,10)
x = (sym) 0.3333333333
>> x=vpa(1/3,15)
x = (sym) 0.333333333333333
>> x=vpa(1/3,16)
x = (sym) 0.3333333333333333
>> x=vpa(1/3,17)
x = (sym) 0.33333333333333331
>> version
ans = 4.0.1
>> uname
ans =
scalar structure containing the fields:
sysname = MINGW32_NT-6.2
nodename = *
release = Windows 6.2
version =
machine = i686
This is the python version I use
Python 3.5.1 (v3.5.1:37a07cee5969, Dec 6 2015, 01:54:25) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
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