Is there any known eason why my level 2 matlab S-function runs slow

Please take a look at the following very simple level 2 matlab S-function, do you please know any reason why it should run slow.

By the way How do I past the matlab code in this textbox so that it can be readable?

/////////////////////////////////////////////////////////////
function handFunctionSeq(block)

setup(block);

function setup(block)

% Register number of ports
block.NumInputPorts  = 1;
block.NumOutputPorts = 4;

% Setup port properties to be inherited or dynamic

% % Override input port properties
block.InputPort(1).Dimensions        = 1;
 block.InputPort(1).DatatypeID  = 0;  % double
 block.InputPort(1).Complexity  = 'Real';
 block.InputPort(1).DirectFeedthrough = true;
% 
% % Override output port properties
%opeing of hand: thumb
 block.OutputPort(1).Dimensions       = 1;
 block.OutputPort(1).DatatypeID  = 0; % double
 block.OutputPort(1).Complexity  = 'Real';
 block.OutputPort(1).SamplingMode = 'sample';

   %opening of hand: fingers
   block.OutputPort(2).Dimensions       = 1;
   block.OutputPort(2).DatatypeID  = 0; % double
   block.OutputPort(2).Complexity  = 'Real';
   block.OutputPort(2).SamplingMode = 'sample';

   %closing if hands: thumb
    block.OutputPort(3).Dimensions       = 1;
   block.OutputPort(3).DatatypeID  = 0; % double
   block.OutputPort(3).Complexity  = 'Real';
   block.OutputPort(3).SamplingMode = 'sample';

   %closing of hand: fingers
    block.OutputPort(4).Dimensions       = 1;
   block.OutputPort(4).DatatypeID  = 0; % double
   block.OutputPort(4).Complexity  = 'Real';
   block.OutputPort(4).SamplingMode = 'sample';

% Register parameters
block.NumDialogPrms     = 4;
block.SampleTimes = [-1 0];
block.SimStateCompliance = 'DefaultSimState';

%%Register methods
block.RegBlockMethod('PostPropagationSetup',@DoPostPropSetup);

block.RegBlockMethod('Outputs',             @Outputs);  
block.RegBlockMethod('Update',              @Update); 
block.RegBlockMethod('Start', @Start);

block.RegBlockMethod('SetInputPortSamplingMode',@SetInputPortSamplingMode);

%end setup

function DoPostPropSetup(block)
block.NumDworks = 1;

    block.Dwork(1).Name            = 'x1';
    block.Dwork(1).Dimensions      = 1;
    block.Dwork(1).DatatypeID      = 0;      % double
    block.Dwork(1).Complexity      = 'Real'; % real
    block.Dwork(1).UsedAsDiscState = true;

function Start(block)

block.Dwork(1).Data =0;

%endfunction

function Outputs(block)
%delays in samples
delay_close_open=block.DialogPrm(1).Data;%e.g=256*3 samples
delay_thumb_close=block.DialogPrm(2).Data;%e.g=70 samples
delay_fingers_open=block.DialogPrm(3).Data;%e.g=70 samples
trialLength=block.DialogPrm(4).Data;%e.g=256*5 samples

block.OutputPort(1).Data=0;
block.OutputPort(2).Data=0;
block.OutputPort(3).Data=0;
block.OutputPort(4).Data=0;

%opening of hands
block.OutputPort(1).Data = block.InputPort(1).Data;%thumb signal sent first
if(block.Dwork(1).Data>=delay_fingers_open)

    block.OutputPort(2).Data =block.InputPort(1).Data;%delayed fingers signal follows 
  else
      block.OutputPort(2).Data=0;

end

%closing of hand
if(block.Dwork(1).Data>=delay_close_open)
    if(block.Dwork(1).Data<=trialLength)%delaying closing of hand in samples
    % disable opeinning of hand when closing hands
        block.OutputPort(1).Data=0;
        block.OutputPort(2).Data=0;

          %initiate closing of hand starting with the fingers
          block.OutputPort(4).Data = block.InputPort(1).Data;%fingers signal sent first
          if(block.Dwork(1).Data>=delay_thumb_close+delay_close_open)

              block.OutputPort(3).Data =block.InputPort(1).Data;%thumb signal comes after
          else
              block.OutputPort(3).Data=0;
          end

      else
          %i.e the going back to opeing of hands. This is the end of the
          %circle so we can go back to hand opening and reseting our work
          %vectors
          block.Dwork(1).Data=0;
          block.OutputPort(2).Data=0;%avoid the spike of channel 2

      end
  else

end

%end Outputs

function Update(block)

block.Dwork(1).Data =block.Dwork(1).Data+1 ;

%end Update

function SetInputPortSamplingMode(s, port, mode)
s.InputPort(port).SamplingMode = mode;

///////////////////////////////////////////////////////////////

[Kaustubha Govind]

I formatted your question for you, but please see http://www.mathworks.com/matlabcentral/answers/7885-tutorial-how-to-format-your-question

[bethel o]

Kaustubha Govind thank you very much!

Answer 1

[Kaustubha Govind]

Your code looks fairly simple, and I don't see anything that stands out, but how do you figure out that it's the S-function that slows down your model? Did you use Simulink Profiler. Note that MATLAB S-functions are executed by using the MATLAB interpreter, which will in general be slower than running other Simulink blocks (which are typically implemented in C/C++). If performance is of utmost importance, and you have narrowed down the performance issue to your S-function, you may want to consider either implementing your S-function in C as a C-MEX S-function, or using an (Embedded) MATLAB Function block. Note that (Embedded) MATLAB Function blocks do not have an Update method, but unless you have a feedback loop involving your S-function, your Update method looks simple enough that you can just add it to the bottom of your Output function.

[bethel o]

Thank you for your answere Kaustubha Govind. Yeah I have tried the s-function block on its own but it runs slow. I guess I should try using C-MEX. About Embedded MATLAB function block, are they fast, they won't have memory(like work vectors) would they?

Thank you very much!

[Kaustubha Govind]

Bethel: Embedded MATLAB Function blocks generate C code for execution, so they are as efficient as C-MEX S-functions. They don't have dwork vectors, but you can work around that by using persistent variables. Please see Using Persistent Variables to Model State.

[bethel o]

Thank you very much. I will try Embedded MATLAB Function blocks.