Software Development

Create Standalone Executables Using Compiled Functions 

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X lopassmainSrc = " #include \"stdio.h\" #include \"stdlib.h\" #include \"lopass.h\" #include \"WolframRTL.h\" static WolframLibraryData libData = 0; int main() { int err = 0; mint i, type, rank, nelems, *dims; double *data; MTensor x, y; double dt; double RC; libData = WolframLibraryData_new(WolframLibraryVersion); /* read x */ type = MType_Real; rank = 1; dims = (mint*)malloc(rank * sizeof(mint)); scanf(\" %d\", &nelems); dims[0] = nelems; err = (*(libData->MTensor_new))(type, rank, dims, &x); if (err) return 1; free(dims); data = (*(libData->MTensor_getRealData))(x); for(i = 0; i < nelems; i++) { scanf(\" %lf\", &(data[i])); } /* read dt */ scanf(\" %lf\", &dt); /* read RC */ scanf(\" %lf\", &RC); err = Initialize_lopass(libData); y = 0; err = lopass(libData, x, dt, RC, &y); printf(\"%d\\n\", err); if(0 == err){ dims = libData->MTensor_getDimensions(y); nelems = dims[0]; data = (*(libData->MTensor_getRealData))(y); printf(\"%d\\n\", nelems); for(i = 0; i < nelems; i++) printf(\"%f\\n\", data[i]); } Uninitialize_lopass(libData); return 0; } ";

Start by defining a function or functions of interest.

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X lopass = Compile[{{x, _Real, 1}, dt, RC}, Module[{a = dt/(RC + dt), yprev = First[x], yi}, Table[yi = a*x[[i]] + (1 - a)*yprev; yprev = yi; yi, {i, 1, Length[x]}]]];

Generate C code and a header.

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X targetDir = CreateDirectory[] fnSource = FileNameJoin[{targetDir, "lopass.c"}]; Export[fnSource, lopass];

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Write a C main function to call the generated code.

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X lopassmainSrcFile = FileNameJoin[{targetDir, "lopassMain.c"}]; Export[lopassmainSrcFile, lopassmainSrc, "Text"]

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Compile it into an executable using the Wolfram Runtime Library.

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X Needs["CCompilerDriver`"]; lopassExe = CreateExecutable[{fnSource, lopassmainSrcFile}, "lowpass", "TargetDirectory" -> targetDir, "Libraries" -> "WolframRTL_Static_Minimal"]

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Now you can distribute the program and run it outside of Mathematica. You can also run it inside Mathematica to test and demonstrate it. Set up an input signal with several frequency components.

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X input = Table[Sin[x] + Sin[x*10] + Sin[x*50], {x, 0, 10, 0.01}]; ListPlot[input, Joined -> True]

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Convert the input signal to the file format that the executable expects.

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X inputText = StringJoin[ToString[Length[input]], "\n", Riffle[ToString /@ input, "\n"],(* dt*)"0.01",(*RC *)"0.3"]; inputFile = FileNameJoin[{targetDir, "input.txt"}]; Export[inputFile, inputText, "Text"]

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Run the executable, parse the output, and plot the original signal (blue) with the low-pass filtered signal (red).

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X SetDirectory[targetDir]; outputLines = Import["!" <> lopassExe <> " < " <> inputFile, "Lines"]; ResetDirectory[]; output = ToExpression /@ outputLines; output = If[ Length[output] > 1 && First[output] === 0 && output[[2]] === Length[output] - 2, Drop[output, 2], $Failed ]; ListPlot[{input, output}, Joined -> True]

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