ILNumerics: ILArray as instance variables;

Question

I am using ILNumerics to represent some time series.

Ideally I would like to have all data incapsulated a la object oriented and, therefore, to use instance variables and instance methods to process such variables.

I have several questions, but all related to what is the best way to implement ILArray in a class, in an efficient way and, possibly, as instance variables. I have gone through the relevant documentation and checked previous SO examples, but none seems to explicitly address these issues.

First: the example proposed on the website for 'Array Utilization Class' [source: http://ilnumerics.net/ClassRules.html] does not seem to compile, at least with ILNumerics trial edition and VS 2013 professional (.net 4.5). Am I missing something?

Or is it because this part of the code:

public ILRetArray<double> A 
{
  get 
  { 
    // lazy initialization 
    if (m_a.IsEmpty) 
    {
       m_a.a = ILMath.rand(100,100); 
    }
  }
  set { m_a.a = value; }

does not have a return statement?

In the mentioned example then the m_a array may be modified through the following instance method:

public void Do() 
{
    using (ILScope.Enter()) 
    {
       // assign via .a property only!
       m_a.a = m_a + 2; 
    }
}

How can one access a specific component of the vector: suppose we want something like m_a[0] = 2.2; would this get in the way of the memory management?

As a general observation, it would seem to me that the natural way of using ILNumerics is through static methods as one would write the code in Fortran (or possibly in R/Matlab): this is how I have used it, so far. Am I right or class definition having ILArray types as instance variables and relevant methods should be as efficient and straightforward?

Alternatively, would you recommend adopting System arrays as instance variables and then importing/exporting to ILarray only through static methods to perform array operation? I would tend to avoid this path or I would like to keep it as confined as possible.

One thing is certain. The property `A` in your code above is not legal because it has a `get` accessor where the end point of the getter body is reachable (there is no `return` anywhere, and nothing (like `throw` or infinite loop) stops the control from flowing to the end of the `get` "block"). A `get` accessor is just like a method whose return type is the type of the property (in particular not `void`). Edit: Maybe they meant to write `return m_a.a;` after the `if` block? — Jeppe Stig Nielsen, Jul 27 '14 at 19:04
Found the page you intended to link (broken link above fixed), and they do have a `return` statement in the end of the `get` accessor. — Jeppe Stig Nielsen, Jul 27 '14 at 19:13
@JeppeStigNielsen yes I think that is what they meant; I guess the type has been fixed by ILNumerics after this post. I had reported it as it was at the time I wrote the post. Thanks for your comment — alea_iacta_est, Jul 27 '14 at 20:06
in my previous comment type --> typo; embarrassing a typo on typo. — alea_iacta_est, Jul 27 '14 at 20:21

Haymo Kutschbach · Accepted Answer · 2014-07-27T20:10:23.707

The documentation section 'ILArray and Classes' has been updated. As you stated, there was a mistake in the sample code.

Modifying ILArray instances as Class Member

By following the rules described in the documentation, all array members will be of type ILArray (or ILLogical or ILCell). These types are mutable types. You can alter them freely during their lifetime. m_a[0] = 2.2; works as expected. You may also decide to replace the array completely:

m_a.a = ILMath.rand(2,3,5);

Just keep in mind, not to simply assign to the array but to use the .a = property or .Assign() method on the array. The compiler will prevent you from mistakenly assigning anyway, since you have declared your array as readonly.

Such alteration does work with the memory management smoothly.

Mixing Static Methods and Class Instances

As long as you keep an eye on the rules for both: functions (ILScope blocks, distinct input parameter array types, assignemens via .a property) and classes (readonly ILArray<T> declaration, ILMath.localMember<T> initialization) you can freely mix both schemes. It will work both ways and reuse all memory not needed anymore immediately.

Mixing intensive use of System.Array with ILArray<T> on the other side may lead to disadvantageous allocation patterns. In general, it is easy to create ILArray from System.Array. The System.Array will be used directly by the ILArray if it fits into the storage scheme (i.e. if it is 1dimensional). But the other way around is not very efficient. It generally involves a copy of the data and the ILNumerics memory management cannot work efficiently either.

That's why we recommend to stay with ILArray and the like. As you see, there are some rules to keep in mind, but usually you will internalize them very quickly.

ILNumerics: ILArray as instance variables;

1 Answers1

Modifying ILArray instances as Class Member

Mixing Static Methods and Class Instances