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Tech:double array - double_array Technical Notes

Declaration 
#include <gridlabd.h>
class myclass : public gld_object {
private:
    GL_STRUCT(double_array,name);
}
Implementation
#include "myclass.h"
myclass::myclass(MODULE *module)
{
   // ...
   if ( gl_publish(oclass,
      PT_double_array,"name",get_name_offset(), // other options...
      NULL)<1 )
      exception("unable to publish module myclass properties");
   // ...
}
int myclass::create(void)
{
   // ...
   name.set_name("name");
   // ...
}
int myclass::init(OBJECT *parent)
{
   // ...
   set_name("'a'11 'a'12 ... 'a'1M ; 'a'21 'a'22 ... 'a'2M ; 'a'N1 'a'N2 ... 'a'NM");
}

The double_array is a built-in type type and implemented as a class in the C++ Module API. This class allows basic math operations on arrays. The following operators are supported

Example

A good example of using double_array is the canonical control model:

int example::sync(timestamp t1)
{
    TIMESTAMP ts = 10; // discrete-time model time step
    Y = C*X + D*U;
    X += A*X + B*U;
    return (t1/ts+1)*ts;
}

The declarations for the arrays are

GL_STRUCT(double_array,A); ///< A matrix (state transition)
GL_STRUCT(double_array,B); ///< B matrix (control)
GL_STRUCT(double_array,C); ///< C matrix (output)
GL_STRUCT(double_array,D); ///< D matrix (feedfwd)
GL_STRUCT(double_array,X); ///< state vector X (state)
GL_STRUCT(double_array,U); ///< control vector U (input)
GL_STRUCT(double_array,Y); ///< output vector Y (output)

The user would then provide the input and output properties and the model definition in the GLM file. The following example is a SISO model (the extension to MIMO is intuitive).

module 
class example {
   double input;
   double output;
}
object example {
   input 0;
   output 0;
   A "0 1 ; -0.16 -1"; // dimensions must match state vector 
   B "1 ; 1"; // dimensions must match state vector and input
   C "1 0"; // dimensions must match state vector and output
   D "0"; // dimensions must match input input and output
   U "input";
   X "0 ; 0";
   Y "output";
   object player {
       property input;
       file input.csv;
   };
   object recorder {
       property output;
       file output.csv;
       interval -1;
   };
};

History

Support for double_array math operations was added in Jojoba (Version 3.2).

See also