mirror of https://github.com/Askill/AP-SCE.git
58 lines
2.0 KiB
C++
58 lines
2.0 KiB
C++
#include "mex.h"
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#include "matrix.h"
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#include "stdlib.h"
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void mexFunction(int nlhs, mxArray *plhs[], // Output variables
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int nrhs, const mxArray *prhs[]) // Input variables
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{
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if (nrhs != 2 || ! mxIsNumeric (prhs[0]))
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mexErrMsgTxt ("Check your input parameters");
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int variables = *mxGetPr(prhs[0]);
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double* x = (double *)mxCalloc(variables+1, sizeof(double)); //create solution array
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double** GA = (double **)mxCalloc(variables+1, sizeof(double*)); //create Gauss Array (GA)
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for (int i = 0; i <= variables; i++){
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GA[i] = (double *)mxCalloc(variables+1, sizeof(double));
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}
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for(int i = 0; i < variables*(variables+1); i++){ //copy input array into GA
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GA[i%variables][i/variables] = mxGetPr(prhs[1])[i];
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}
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// Gauß
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for (int i = 0; i<variables; i++) //Pivotisation
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for (int k = i + 1; k<variables; k++)
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if (abs(GA[i][i])<abs(GA[k][i]))
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for (int j = 0; j <= variables; j++)
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{
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long double temp = GA[i][j];
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GA[i][j] = GA[k][j];
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GA[k][j] = temp;
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}
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for (int i = 0; i<variables - 1; i++) //gauss elimination
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for (int k = i + 1; k<variables; k++)
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{
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long double t = GA[k][i] / GA[i][i];
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for (int j = 0; j <= variables; j++)
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GA[k][j] = GA[k][j] - t*GA[i][j]; //make the elements below the pivot elements equal to zero or elimnate the variables
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}
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for (int i = variables - 1; i >= 0; i--) //back-substitution
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{ //x is an array whose values correspond to the values of x,y,z..
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x[i] = GA[i][variables]; //make the variable to be calculated equal to the rhs of the last equation
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for (int j = i + 1; j<variables; j++)
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if (j != i) //then subtract all the lhs values except the coefficient of the variable whose value is being calculated
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x[i] = x[i] - GA[i][j] * x[j];
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x[i] = x[i] / GA[i][i]; //now finally divide the rhs by the coefficient of the variable to be calculated
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}
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//Output
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nlhs = 1;
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plhs[0] = mxCreateDoubleMatrix(1, variables, mxREAL);
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memcpy(mxGetPr(plhs[0]), x, variables*sizeof(double));
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return;
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} |