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→Why is Octave's floating-point computation wrong?
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* Search for an answer in our [https://lists.gnu.org/archive/html/help-octave/ mailing list archives] | * Search for an answer in our [https://lists.gnu.org/archive/html/help-octave/ mailing list archives] | ||
* Contact our user community using our [https:// | * Contact our user community using our [https://octave.discourse.group Octave Discourse]. | ||
* Contact our user community using our [https://webchat.freenode.net/?channels=octave IRC chat room <code>#octave</code> in Freenode] | * Contact our user community using our [https://webchat.freenode.net/?channels=octave IRC chat room <code>#octave</code> in Freenode] | ||
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John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring ({{Release Year}}). | John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring ({{Release Year}}). | ||
GNU Octave version {{Release}} manual: a high-level interactive language for numerical computations. | GNU Octave version {{Release}} manual: a high-level interactive language for numerical computations. | ||
URL https:// | URL https://octave.org/doc/v{{Release}}/ | ||
A [https://en.wikipedia.org/wiki/BibTeX BibTeX] entry for [https://en.wikipedia.org/wiki/LaTeX LaTeX] users is: | A [https://en.wikipedia.org/wiki/BibTeX BibTeX] entry for [https://en.wikipedia.org/wiki/LaTeX LaTeX] users is: | ||
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author = {John W. Eaton and David Bateman and S{\o}ren Hauberg and Rik Wehbring}, | author = {John W. Eaton and David Bateman and S{\o}ren Hauberg and Rik Wehbring}, | ||
year = <span>{</span>{{Release Year}}}, | year = <span>{</span>{{Release Year}}}, | ||
url = {https:// | url = {[https://octave.org/doc/v{{Release}}/ https://octave.org/doc/v{{Release}}/]}, | ||
} | } | ||
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The following steps have been the solution to several bug reports and help requests. Please try them before asking for further support. If nothing below helps, please give us the following information: | The following steps have been the solution to several bug reports and help requests. Please try them before asking for further support. If nothing below helps, please give us the following information: | ||
* Operating system: e.g. [https://support.microsoft.com/en-us/help/13443/windows-which-version-am-i-running '''Windows 10 (version | * Operating system: e.g. [https://support.microsoft.com/en-us/help/13443/windows-which-version-am-i-running '''MS Windows 10 (version 2004)'''] or '''Ubuntu 20.04''' | ||
* GNU Octave version: e.g. '''Version {{Release}}''' | * GNU Octave version: e.g. '''Version {{Release}}''' | ||
* Installation method: e.g. '''Downloaded and installed "octave-{{Release}}-w64-installer.exe" from https://www.octave.org/download.html''' | * Installation method: e.g. '''Downloaded and installed "octave-{{Release}}-w64-installer.exe" from https://www.octave.org/download.html''' | ||
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* After Octave upgrade the GUI does not open / shuts down immediately. | * After Octave upgrade the GUI does not open / shuts down immediately. | ||
** '''Solution:''' Delete the folder {{path|C:\Users\YOUR_USER_NAME\.config\octave}} | ** '''Solution:''' | ||
*** Version 5.2.0 and older: Delete the folder {{path|C:\Users\YOUR_USER_NAME\.config\octave}} | |||
*** Version 6.1.0 and newer: Delete the folder {{path|%APPDATA%\octave}}, which generally is located at {{path|C:\Users\YOUR_USER_NAME\AppData\Roaming\octave}} | |||
* Missing/conflicting files. | * Missing/conflicting files. | ||
** '''Solution:''' Remove/Uninstall all existing Octave versions. Restart the system. Install GNU Octave again. | ** '''Solution:''' Remove/Uninstall all existing Octave versions. Restart the system. Install GNU Octave again. | ||
* Permission errors. | |||
** '''Solution | * Permission errors | ||
** '''Solution | ** '''Solution 1:''' Octave on MS Windows uses VBS scripts to start the program. You can test whether your system is blocking VBS scripts by doing the following: | ||
**# Using Notepad or another text editor, create a text file containing only the text: <pre>msgbox("This is a test script, Click OK to close")</pre> | |||
**# Save the file on your Desktop with the name {{Path|testscript.vbs}} (be sure that the editor didn't end it in .txt or .vbs.txt). | |||
**# Double click the file. If scripts can run, a popup window will appear with that message. | |||
**#* If the file opens in notepad or an editor, it means it still ended in .txt. MS Windows insecurely hides file extensions by default. To show file extensions follow [https://answers.microsoft.com/en-us/windows/forum/all/in-win10-how-to-show-the-file-extension-for/ed21ff20-cdb3-4263-9c7d-fc6ed125fc82 these instructions at Microsoft.com]. | |||
**#* If both {{Path|testscript.vbs}} and {{Path|octave.vbs}} open a text- or other editor, it means your MS Windows file associations have .vbs files associated with another program. To fix this, right click the .vbs file, select "Open With", select "Choose Another App", check the box that says "Always use this app to open .vbs files". Finally, select "Microsoft Windows Based Script Host" from the list. If it is not in the list, select "More apps". If still not there, select "Look for Another App on this PC" and navigate to {{Path|C:\Windows\System32\wscript.exe}}, select it, and select "Open". If {{Path|wscript}} is still not present you will need to seek assistance installing missing MS Windows components. | |||
**# Try moving {{Path|testscript.vbs}} to another location, such as a {{Path|C:\temp folder}}. Additionally try to move {{Path|testscript.vbs}} in the Octave installation folder containing {{Path|octave.vbs}} and see if VBS scripts can be run there. | |||
**# If {{Path|testscript.vbs}} doesn't run in any of those locations, then scripting appears to be disabled or blocked on your system. If {{Path|testscript.vbs}} runs in some locations but not others, there there may be other security permissions errors to be solved. If {{Path|testscript.vbs}} runs in the same folder as {{Path|octave.vbs}}, but directly double-clicking on {{Path|octave.vbs}} does not start Octave, then there appears to be some problem other than script permissions. | |||
** '''Solution 2:''' Consult your malware detection (a.k.a. AntiVirus) software, if files are blocked. | |||
** '''Solution 3:''' Did you install Octave on a network-drive? Do you have the execution permissions? | |||
** '''Solution 4:''' Is your computer managed by your company? Does your administrator prohibit script execution? | |||
==I do not see any output of my script until it has finished?== | ==I do not see any output of my script until it has finished?== | ||
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==Why is Octave's floating-point computation wrong?== | ==Why is Octave's floating-point computation wrong?== | ||
Floating-point arithmetic is an approximation '''in binary''' to arithmetic on real or complex numbers. Just like you cannot represent 1/3 exactly in decimal arithmetic (0.333333... is only a rough approximation to 1/3), you cannot represent some fractions like <math>1/10</math> exactly in base 2. In binary, the representation to one tenth is <math>0.0\overline{0011}_b</math> where the bar indicates that it repeats infinitely (like how <math>1/6 = 0.1\overline{6}_d</math> in decimal). Because this infinite repetition cannot be represented exactly with a finite number of digits, rounding errors occur for values that appear to be exact in decimal but are in fact approximations in binary, such as for example how 0.3 - 0.2 - 0.1 is not equal to zero. | Floating-point arithmetic is an approximation '''in binary''' to arithmetic on real or complex numbers. Just like you cannot represent 1/3 exactly in decimal arithmetic (0.333333... is only a rough approximation to 1/3 for any finite number of 3s), you cannot represent some fractions like <math>1/10</math> exactly in base 2. In binary, the representation to one tenth is <math>0.0\overline{0011}_b</math> where the bar indicates that it repeats infinitely (like how <math>1/6 = 0.1\overline{6}_d</math> in decimal). Because this infinite repetition cannot be represented exactly with a finite number of digits, rounding errors occur for values that appear to be exact in decimal but are in fact approximations in binary, such as for example how 0.3 - 0.2 - 0.1 is not equal to zero. | ||
In addition, some advanced operations are computed by approximation and there is no guarantee for them to be accurate, see [https://en.wikipedia.org/wiki/Rounding#Table-maker.27s_dilemma Table-maker's dilemma] for further references. Their results are system-dependent. | In addition, some advanced operations are computed by approximation and there is no guarantee for them to be accurate, see [https://en.wikipedia.org/wiki/Rounding#Table-maker.27s_dilemma Table-maker's dilemma] for further references. Their results are system-dependent. | ||
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This is one of those times where the best documentation is to read the existing code. We have three different toolkits in Octave now, so there are some examples to draw from. | This is one of those times where the best documentation is to read the existing code. We have three different toolkits in Octave now, so there are some examples to draw from. | ||
=Development | = Development = | ||
== When will feature X be released or implemented? == | |||
When it's ready, sooner [https://www.octave.org/get-involved.html if you help]. You can [https://savannah.gnu.org/patch/?group=octave send us patches] if you can implement feature X yourself. If you can't, some [https://www.octave.org/commercial-support.html developers may be convinced to work on your specific problem for some money]. | |||
== How can I get involved in Octave development? == | |||
:''See [[Developer FAQ]]''. | |||
[[Category:FAQ]] | |||