Port Dimensions Error in S-Function

Hello,

I'm trying to make an S-function that will perform the element wise multiplication of two vectors, in fact, I want to replicate the "Product" block with an S-Function.

I'm trying to start simple so my code doesn't feature matrix multiplication yet, since I think that that part will be quite trivial once I get the port dimensions working.

I'm getting the following error when I try to use a size 4 vector and a size 1 vector:

Error in port widths or dimensions. Output port 1 of 'untitled/Constant1' is a one dimensional vector with 1 elements.
Component:Simulink | Category:Model error
Error in port widths or dimensions. Input port 2 of 'untitled/S-Function7' is a one dimensional vector with 4 elements.
Component:Simulink | Category:Model error

I want the input and output ports to be dynamically sized so that I can input a vector of any size that will be multiplied by a vector of the same size or size 1.

As a result my code is as follows:

static void mdlInitializeSizes(SimStruct *S)
{


    ssSetNumSFcnParams( S, 0); /*number of input arguments*/

    if (!ssSetNumInputPorts(S, 2)) return;
    ssSetInputPortWidth(S, 0, DYNAMICALLY_SIZED);
	ssSetInputPortWidth(S, 1, DYNAMICALLY_SIZED);
    ssSetInputPortDirectFeedThrough(S, 0, 1);
    ssSetInputPortDirectFeedThrough(S, 1, 1);


    if (!ssSetNumOutputPorts(S,1)) return;
    ssSetOutputPortWidth(S, 0, DYNAMICALLY_SIZED);
    
    ssSetNumSampleTimes( S, 1);
	
}

static void mdlInitializeSampleTimes(SimStruct *S)
{
    ssSetSampleTime(S, 0, INHERITED_SAMPLE_TIME);
    ssSetOffsetTime(S, 0, 0.0);
} 
static void mdlOutputs(SimStruct *S, int_T tid)
{
    real_T            *y    = ssGetOutputPortRealSignal(S,0);
	 *y = 5; /* %This is of course just a placeholder for the algorithm I'll be using' 
 }

Only the mdlInitializeSizes(SimStruct *S) executes before I get an error but I don't understand why. In the model, when I run it, the second input port of the S-function, is expecting a size 4 vector as input when I'm giving it a size 1 vector. But why is it expecting so? Thanks in advance for any help

[Suman]

Hi,

Please refer to the MATLAB Answers:

• https://www.mathworks.com/matlabcentral/answers/248904-error-in-port-widths-or-dimensions
• https://www.mathworks.com/matlabcentral/answers/569154-rectifying-port-width-error