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162 bytes removed ,  16:09, 17 March 2018
Updated links and developer information, added reference to other IEEE 1788 software and new IEEE Std 1788.1
<div style="float: right; margin: 0 3em">[[File:Octave-interval.png|center]]</div>The GNU Octave interval package for real-valued [ interval arithmetic].
[[File:Interval-sombrero.png|280px|thumb|right|Plotting the interval enclosure of a function]]
== Distribution ==
* [httphttps://octave.sourceforge.netio/interval/index.html Latest version at Octave Forge]
** <code>pkg install -forge interval</code>
** [httphttps://octave.sourceforge.netio/interval/overview.html function reference]** [httphttps://octave.sourceforge.netio/interval/package_doc/index.html package documentation] (user manual)
* [ Debian GNU/Linux], [ Launchpad Ubuntu]
* [ archlinux user repository]
* Included in [ official Windows installer] and installed automatically with Octave (since version 4.0.1)
* [ / MacPorts] for Mac OS X* [http FreshPorts] for FreeBSD
* [ Cygwin] for Windows
* [ openSUSE build service]
== Development status ==
* Completeness
** All required functions from [ IEEE Std 1788-2015], IEEE standard for interval arithmetic, are implemented. The standard was approved by IEEE-SA on June 11, 2015. It will remain active for ten years. The standard was approved by ANSI in 2016.** Also, the minimalistic standard [ IEEE Std 1788.1-2017], IEEE standard for interval arithmetic (simplified) is fully implemented. The standard was approved by IEEE-SA on December 6, 2017 (and published in January 2018).** In addition there are functions for interval matrix arithmetic, N-dimensional interval arrays, plotting , and solvers.
* Quality
** Most arithmetic operations produce tight, correctly-rounded results. That is, the smallest possible interval with double-precision (binary64) endpoints, which encloses the exact result.** Includes tests [ large test suite] for all functions, many tests for basic arithmetic functions** No known For open bugs please refer to the [ bug tracker].* Performance** All elementary functions have been [ vectorized] and run fast on large input data. The package ** Arithmetic is quite new and still has a small user baseperformed with the [ GNU MPFR] library internally. Where possible, so there might be hidden bugsthe optimized [ Also some advanced functions will always need more testingfr/www/crlibm/ CRlibm] library is used.
* Portability
** Runs in GNU Octave ≥ 3.8.2
** Known to run under GNU/Linux, Microsoft Windows, macOS, and FreeBSD
* Possible == Project ideas (TODOs) ==** To be considered in the future: Algorithms can be migrated from the C-XSC Toolbox (C++ code) from [] (nlinsys.cpp and cpzero.cpp), however these would need gradient arithmetic and complex arithmetic.** Interval version of <code>interp1</code>** Extend <code>subsasgn</code> to allow direct manipulation of inf and sup (and dec) properties.
>> A = infsup ("[2, 4]");
>> A.inf = infsup ("[1, 3]")
>> A.inf.inf = 42 # should produce error?
>> A.inf.sup = 42 # should produce error?
:* Tight Enclosure of Matrix Multiplication with Level 3 BLAS [] []:* Verified Convex Hull for Inexact Data [] []:* Implement user-controllable output from the interval standard (e. g. via printf functions):
a) It should be possible to specify the preferred overall field width (the length of s).
b) It should be possible to specify how Empty, Entire and NaI are output,
== Compatibility ==
The interval package's main goal is to be compliant with IEEE Std 1788-2015, so it is compatible with other standard-conforming implementations (on the set of operations described by the standard document).Other implementations, which are known to aim for standard conformance are: * [ IntervalArithmetic.jl package] (Julia)* [ JInterval library] (Java)* [ ieeep1788 library] (C++) created by Marco Nehmeier, later forked by Dmitry Nadezhin
=== Octave Forge simp package ===
* Basic operations can be found in both packages, but the availability of special functions depends
 <div style="display:flex; align-items: flex-start"><div style="margin-right: 2em">{{Code|In GNU Octave the Computation with this interval package can also be run alongside INTLAB.|<syntaxhighlight lang="octave"> # INTLAB intervalspkg load interval A1 = infsup (2, 3); B1 = hull (-4, A1A2); C1 = midrad (0, 2); # Interval package intervals pkg load intervalA1 + B1 * C1</syntaxhighlight>}}</div><div>{{Code|Computation with INTLAB|<syntaxhighlight lang="octave">startintlab A2 = infsup (2, 3); B2 = hull (-4, A2); C2 = midrad (0, 2); pkg unload interval # Computation with INTLAB A1 + B1 * C1 # Computation without INTLAB A2 + B2 * C2
==== Known differences ====
| isintval (x)
== Similar software ==
For C++ there is an interval library [ libieeep1788] by Marco Nehmeier (member of IEEE P1788). It aims to be standard compliant with IEEE Std 1788-2015 and is designed in a modular way, supporting several interval data types and different flavors of interval arithmetic []. The GNU Octave interval package shares several unit tests with libieeep1788.
For Julia there is an evolving interval library [ ValidatedNumerics.jl] by Luis Benet and David P. Sanders. It is planned to become conforming to IEEE Std 1788-2015 (or to the basic standard 1788.1) in the future.
== Developer Information ==
'''Build dependencies'''
<code>apt-get install libmpfr-dev autoconf automake git python3-ply python3-yaml inkscape zopfli</code> * Octave* Mercurial* Texinfo* MPFR* Octave package: doctest** Purpose: Verification of the examples in the manual and in the function documentation** Installation: Use <code>pkg install -forge doctest</code> inside Octave* Octave package: generate_html** Purpose: Generate HTML documenation for publication on Octave Forge (only needed for release)** Installation: Use <code>pkg install -forge generate_html</code> inside Octave* Autoconf & Automake** Purpose: Preparation of bundled crlibm library for a release* ITF1788** Purpose: Compilation of unit-test** Installation: The git repository is automatically cloned by the Makefile* Inkscape** Purpose: Generate / convert images for the manual* Zopfli** Purpose: Optimize the size of the compressed release tarball
=== Architecture ===
| | `- ... – further functions on decorated intervals
| `- ... – a few global functions that don't operate on intervals
+`- src/ | | +- – computes various arithmetic functions correctly rounded (using MPFR) | | `- ... – other oct-file sources `- test/ – interval arithmetic unit tests
=== Best practices ===
Octave functions may be used as long as they don't introduce arithmetic errors. For example, the ceil function can be used safely since it is exact on binary64 numbers.
function x = ceil (x)
... parameter checking ... x.inf = ceil (x.inf); x.sup = ceil (x.sup);
All functions should be implemented using vectorization and indexing. This is very important for performance on large data. For example, consider the plus function. It computes lower and upper boundaries of the result (x.inf, y.inf, x.sup, y.sup may be vectors or matrices) and then uses an indexing expression to adjust values where empty intervals would have produces problematic values.
function x = plus (x, y)
... parameter checking ... l = mpfr_function_d ('plus', -inf, x.inf, y.inf); u = mpfr_function_d ('plus', +inf, x.sup, y.sup);
emptyresult = isempty (x) | isempty (y); l(emptyresult) = inf; u(emptyresult) = -inf;


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