Get UTC Time in Generated Code

Question

Michael 2023-8-14

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2008542-get-utc-time-in-generated-code

回答： Corey Silva 2023-9-19

I need to get UTC time down to miliseconds at least (i.e. 1692039433503685.321 seconds) in a piece of generated code C++ code. Unfortunately, Coder doesn't support the 'TimeZone' inputs in datetime, otherwise I'd just use posixtime( datetime('now','TimeZone','UTC') ).

I tried using coder.ceval to call the fuctions in the chono C++ library, but the UTC clock there is only available in the C++20 language standard and Matlab only supports up to C++11.

Is there a good way of doing this?

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Rik 2023-8-15

在 MATLAB Online 中打开

There is a UTC in C. Can you use that?

My getUTC function doesn't support code generation, but it does include this C function:

utc_time_c={'#include "mex.h"';
        '#include "time.h"';
        '';
        '/* Abraham Cohn,  3/17/2005 */';
        '/* Philips Medical Systems */';
        '';
        'void mexFunction(int nlhs, mxArray *plhs[], int nrhs,';
        '                 const mxArray *prhs[])';
        '{';
        '  time_t utc;';
        '  ';
        '  if (nlhs > 1) {';
        '    mexErrMsgTxt("Too many output arguments");';
        '  }';
        '  ';
        '  /* Here is a nice ref: www.cplusplus.com/ref/ctime/time.html */';
        '  time(&utc);';
        '  /* mexPrintf("UTC time in local zone: %s",ctime(&utc)); */';
        '  /* mexPrintf("UTC time in GMT: %s",asctime(gmtime(&utc))); */';
        '  ';
        '  /* Create matrix for the return argument. */';
        '  plhs[0] = mxCreateDoubleScalar((double)utc);';
        '   ';
        '}'};

Denis Gurchenkov 2023-9-18

Hi Mike, I don't have an answer to the main questipn you have, but one possible avenue for progress is to use the C++ 20 functions.

You said that "MATLAB Coder only supports up to C++11" - that is not quite correct. Coder-generated code should work just fine with C++20. The page you referred to just says "coder does not know how to use the C++20 features - at most, it'll generate code using C++11 features". But since C++ standards are generally forward compatible, you should be able to just set the language flag for the C++ compiler. If you add the following line to your matlab function:

coder.updateBuildInfo('addCompileFlags','/std:c++20');

and generate code using "codegen ... -lang:C++" then you should /std:c++20 added to the c compiler command line.

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