How to initialize a string variable, and pass it to the matlab function using GPU coder

How to initialize a string in custom main.cu file and pass it to the matlab function using GPU coder? I tried to look into Matlab documentation, I could not find any references. i hope any of the experts help.

i try to compile the Nivida exectuable file using the matlab function,

function out = test_predict(img,SS)

%SS is a string type e.g. SS="ABCD";

persistent mynet1;

persistent mynet2;

if (strncmp(SS,"GR1",2)==true) && isempty(mynet1)

a1='DLmodel1.mat';

mynet1 = coder.loadDeepLearningNetwork(a1);

out=predict(mynet1,img);

else

a2='DLmodel2.mat';

mynet2 = coder.loadDeepLearningNetwork(a2);

out=predict(mynet2,img);

end

The example main.cu file is created as below:

...

// Function Declarations

static void argInit_1x4_char_T(char result[4]);

static void argInit_299x299x3_real32_T(float result[268203]);

static char argInit_char_T();

static float argInit_real32_T();

static coder::rtString argInit_rtString();

static void main_test_predict();

// Function Definitions

static void argInit_1x4_char_T(char result[4])

{

// Loop over the array to initialize each element.

for (int idx1{0}; idx1 < 4; idx1++) {

// Set the value of the array element.

// Change this value to the value that the application requires.

result[idx1] = argInit_char_T();

}

}

static void argInit_299x299x3_real32_T(float result[268203])

{

// Loop over the array to initialize each element.

for (int idx0{0}; idx0 < 299; idx0++) {

for (int idx1{0}; idx1 < 299; idx1++) {

for (int idx2{0}; idx2 < 3; idx2++) {

// Set the value of the array element.

// Change this value to the value that the application requires.

result[(idx0 + 299 * idx1) + 89401 * idx2] = argInit_real32_T();

}

}

}

}

static char argInit_char_T()

{

return '?';

}

static float argInit_real32_T()

{

return 0.0F;

}

static coder::rtString argInit_rtString()

{

coder::rtString result;

// Set the value of each structure field.

// Change this value to the value that the application requires.

argInit_1x4_char_T(result.Value);

return result;

}

static void main_test_predict()

{

static float b[268203];

coder::rtString c;

float out_data[28];

int out_size[2];

argInit_299x299x3_real32_T(b);

c = argInit_rtString();

testdefclass_predict(b, &c, out_data, out_size);

}

int main(int, char **)

{

// The initialize function is being called automatically from your entry-point

// function. So, a call to initialize is not included here. Invoke the

// entry-point functions.

// You can call entry-point functions multiple times.

//SS is a variable and read out from a text file

FILE *fp= fopen('flile1.txt',r);

char SS[5]="ABCD";

main_test_predict();

// Terminate the application.

// You do not need to do this more than one time.

test_predict_terminate();

return 0;

}

// End of code generation (main.cu)

Can you please

Answer 1

[Joss Knight]

MATLAB and Simulink code generation do not currently support string.

Edit: Sorry, my bad, it does support scalar strings, but not string arrays.

[Liwei]

appreciate the feedback. The char worked.

Answer 2

[Hariprasad Ravishankar]

Hi Liwei,

Do you really need a string data type here? Usually its easier to work with char datatype as input to an entry point function.

For example, for the following entry point function

function out = foo(in)

out = strcmp(in,"apple");

end

>> codegen foo -args {'mango'} -config:dll

Coder generates:

boolean_T foo(const char in[5])

And you can pass a char array as input to the entry point:

void main_foo(void)

{

char cv[5];

boolean_T out;

/* Initialize function 'foo' input arguments. */

/* Initialize function input argument 'in'. */

/* Call the entry-point 'foo'. */

argInit_1x5_char_T(cv);

out = foo(cv);

}

Further, if you know that the input will be a constant at codegen time and won't change at runtime, you can specify it as a constant using the codegen command:

>> codegen foo -args {coder.Constant('mango')} -config:dll

This way you will not have to pass it as input to the generated function from your main()

Answer 3

[Liwei]

Thank you. "passing char" suggestion helps. can you give a clue how to intialize the char? Is this the correct way below?

static void argInit_1x4_char_T(char result[4],char SS[4])
{
    // Loop over the array to initialize each element.
    for (int idx1{0}; idx1 < 4; idx1++) {
    // Set the value of the array element.
    // Change this value to the value that the application requires.
    result[idx1] = SS[idx1];
    }
    }

[Walter Roberson]

In a situation like that, why not use memcpy() ? Unless, that is, that SS and result are different datatypes.

Question: are you using MATLAB char() or C's char ? The difference being that MATLAB char can handle code points > 255. And that for C, strictly speaking char could be signed . (Historically, the fact that char was signed was taken advantage of in some early compilers to return -1 indicating end-of-file using the same datatype as regular outputs. This was not sustainable for binary inputs, but it did happen.)

[Liwei]

thanks for the question.

SS and results, i defined them as the same type in main.cu. Not sure how to intialize them in static void argInit_1x4_char_T(char result[4],char SS[4]). Can you show how you want to use memcpy()?

[Walter Roberson]

static void argInit_1x4_char_T(char result[4],char SS[4]) {
  memcpy(result, SS, 4);
}