faq.english.html

This is svd source code implementation in c++ , the zip file contain the ap file ,more detail ,plea

<h1>General Questions on source codes</h1>

<a name=reliability><h2>How reliable is the ALGLIB package?</h2></a>

<p align=justify>
The following measures are taken to ensure the reliability of the ALGLIB package:
</p>

<ul>
<li>
testing of package algorithms. All modules that have 'development' or 'stable' status have unit tests. Testing of ALGLIB for C#, C++, C++ (multiple precision) and Delphi is carried out automatically. Unfortunately the VBA version is tested manually and not completely, as VBA programs cannot be launched from command line. To compensate for this, the VBA version is actively used to develop new programs, which allows for counting on its stability.
</li>
<li>
a clear specification of modules limitations.
</li>
<li>
a clear differentiation between stably working modules tested by unit tests and time and experimental modules, where the stability is not tested adequately.
</li>
<li>
transparent bug registration and correction processes.
</li>
</ul>

<a name=ap><h2>What is the AP library?</h2></a>

<p align=justify>
AP library is a generic name for a set of libraries in several programming languages performing low-level tasks depending on specific programming languages. The AP library carries out tasks such as working with dynamic one- and multidimensional arrays in languages which do not support this data type, contains implementation of basic linear algebra algorithms, etc. The library is distributed as source codes under BSD license. The library is attached to each algorithm package available for downloading from the web-site. The latest library version is available for downloading from <a href="http://alglib.sources.ru/translator/aplib.zip">http://alglib.sources.ru/translator/aplib.zip</a>
</p>

<a name=ablas><h2>What is the ABLAS library?</h2></a>

<p align=justify>
ABLAS is an optimized implementation of basic linear algebra subroutines written in assembler. To use ABLAS it is necessary to copy the DLL file to one of the system folders or in the program folder and turn on ABLAS support (as described in ABLAS manual). When launching a program that is using the ALGLIB package, the ABLAS library is automatically detected and loaded. If ABLAS is absent, the program uses the standard implementation of linear algebra operations, written in a high-level language. At <a href="http://www,alglib.net/projects/ablas/">http://www,alglib.net/projects/ablas/</a> (or <a href="http://alglib.sources.ru/projects/ablas/">http://alglib.sources.ru/projects/ablas/</a> in Russian) there is library description, the list of the supported platforms and programming languages as well as source code and precompiled binary files.
</p>

<a name=stablevsfull><h2>What is the difference between alglib.stable and alglib.full archives?</h2></a>

<p align=justify>
A 'stable' archive contains only 'stable' modules . A 'full' archive also contains modules with 'experimental' and 'development' status.
</p>

<a name=statuses><h2>What do module statuses (experimental, development, stable, obsolete) mean?</h2></a>

<p align=justify>
Modules included into ALGLIB can have a different status depending on the lifecycle stage they are in:
</p>

<ul>
<li>
<B>experimental</B> - the module is experimental and its stability is not guaranteed. It cannot be used in the programs where high level of reliability is a requirement, but still can be useful for library users. You can use it at your own discretion - for instance, for educational purposes. This status is assigned very rarely and only when an unstable module is still better than no module at all. 
</li>
<li>
<B>development</B> - the module is usable, there are no stability issues, but the API that is offered is not yet a hundred per cent completed. It is possible that in future versions of ALGLIB the module will be changed in the manner not compatible with the previous version. This status is assigned pretty seldom and only to new modules. 
</li>
<li>
<B>stable</B> - the module is usable, there are no stability issues, the API that is offered is absolutely done and will not change. Most often the modules are openly published only after they are assigned 'stable' status.
</li>
<li>
<B>obsolete</B> - the module is not supported anymore and not included in the ALGLIB releases.
</li>
</ul>

<a name=rcomm><h2>Why do some algorithms (for instance, optimization methods) use reverse communication instead of function pointers, delegates and other means of my programming language?</h2></a>

<p align=justify>
Optimization, integration and other similar methods are united by one common trait. They need to have a way of calculating the meaning of a function defined by the <I>user</I> at a point defined by the <I>method</I>.
</p>

<p align=justify>
The most convenient way of solving this problem is transferring a function pointer into the module. However bear in mind that ALGLIB package is written using pseudo code that is automatically translated into different programming languages. While each language has its own function pointer analog that is often different from other languages. When the ALGLIB pseudo code was developed, at some point is became clear that adding function pointers in it will be very complex as this feature is implemented differently in every language. This is why reverse communication was chosen as a different kind of solution.
</p>

<h1>General questions</h1>

<a name=project><h2>What is ALGLIB aimed at?</h2></a>

<p align=justify>
It is mostly aimed at creating a convenient and efficient multilingual scientific software library.
</p>

<a name=diff><h2>What is the difference between ALGLIB and other similar projects?</h2></a>

<p align=justify>
The ALGLIB package:
</p>

<ul>
<li>is a multilingual project. The main feature of the project is that each algorithm is represented by programs in several languages and the language list is the same for every algorithm. This is the main advantage of the site before other similar collections - one algorithm, several languages, identical functionality in each language.</li>
<li>is a collection of programs. Sometimes visitors complain that there are practically no algorithm descriptions at the site. Yes, that's true - just because ALGLIB is a collection of programs, not the used algorithm descriptions. Unfortunately we cannot do everything.</li>
<li>is focused on numerical analysis. There are some other directions in the project (for instance, there are algorithms for sorting and graphics) but numerical analysis is a priority.</li>
<li>is easy to use. To use the ALGLIB package you don't need to learn an unknown programming language, attach additional external libraries or work with an extensive and inconvenient interface to a code written in another programming language.</li>
</ul>

<p align=justify>
Now on what ALGLIB is not and is not going to be. ALGLIB doesn't:
</p>

<ul>
<li>compete with specialized projects. This is not the goal. And, however hard I try, the project won't get as fast as MKL or have as wide a functionality as LAPACK.</li>
<li>go out of the boundaries of the project. For instance, parallel calculations are very interesting, but the solution of this problem is usually tightly connected to a certain platform, programming environment or language, which doesn't align with the main idea of the project.</li>
</ul>

<a name=authors><h2>Who are the authors of the ALGLIB?</h2></a>

<p align=justify>
The first version of ALGLIB was made by Vladimir Bystritsky. He spent a number of years on the maintenance of the website by himself. Eventually, he lost his interest in the website, so I (Sergey Bochkanov) took over the work on its maintenance, by common agreement.
</p>

<a name=rus><h2>What relation does the website have to Russia?</h2></a>

<p align=justify>
Originally, ALGLIB was a Russian-language website. Later on, a part of the website was translated into English. At present, there are two versions of the site - Russian and English.
</p>

<a name=algopascal><h2>What is AlgoPascal?</h2></a>

<p align=justify>
AlgoPascal is a programming language, designed particularly for this project. The programs, written in this language, are processed by a server-side automatic translator and translated into other programming languages by the computer. More detailed information is provided in section <a href="http://www.alglib.net/aboutsite.php">"About the site"</a>.
</p>

<a name=other><h2>Where can I find the algorithms for the work with files, drawing pictures in OpenGL, etc?</h2></a>

<p align=justify>
As we noted before, the main goal of ALGLIB is to create a multilingual library of algorithms in the area of numerical analysis. The problems, related to those enumerated in the question, do not fall into this category. Exceptions are made for a number of problems, though the project can be characterized by a clear-cut specialization.
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