National-instruments AutoCode NI MATRIX Manuale Utente Scaricare il pdf (Pagina 138)

Chapter 5 Generated Code Architecture

AutoCode Reference 5-30 ni.com

In Example 5-9, a hard-subscript, i, is used to access both inputs and

outputs. The reason

i is a hard-subscript is that the range of i—that is,

the values of 1 through to the number of inputs (

u.size)—is known when

the code is generated. AutoCode then can unroll the loop so as to translate

y(i) into a single scalar variable for each value of i. The same is true

for

u(i).

Example 5-9 Hard-Subscript Used to Access an Array

Inputs: u;

Outputs: y;

float u(:), y(u.size);

integer i;

for i = 1:u.size do

y(i) = u(i) * 2*i;

endfor;

In Example 5-10, a soft-subscript, j, is being used to access both inputs and

outputs. That script will not generate code. The reason

j is a soft-subscript

is that the range of

j, that is, the values of 1 through to the value of the first

input

u(1), is not known when code is generated because the upper-bound

j’s range is the value of the first input. Because the range of j is not

known, AutoCode cannot unroll the loop so as to translate the input/output

arrays into their scalar representation.

Example 5-10 Soft-Subscript Example

Inputs: u;

Outputs: y;

integer u(:), y(u.size);

integer j;

for j = 1:u(1)do

y(j) = u(j) + j;

endfor;

Rolling Loops with Scalar Code Generation

Although inputs, outputs, and states are translated into scalars, parameters

and local variables of the BlockScript can be either scalar or array variables

in the generated code. Thus, a common trick has been to copy the inputs

and outputs into local variables that are arrays and use those variables for

the algorithm. Refer to Example 5-11.

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National-instruments AutoCode NI MATRIX Manuale Utente Pagina 138

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