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det2x2.c
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Wed, May 28, 20:14

det2x2.c
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#include <math.h>
#include <mex.h>
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
/*declare variables*/
const mwSize *dims;
mwSize *dimsout;
mwIndex indx;
int i, numdims;
int numelin;
mxClassID classid;
double *input1r, *input1i, *output1r, *output1i;
double a, b, c, d;
double ai, bi, ci, di;
/*figure out the classid*/
classid = mxGetClassID(prhs[0]);
/*check inputs*/
if (nrhs>1)
mexErrMsgTxt("Too many input arguments");
/*associate inputs*/
input1r = mxGetData(prhs[0]);
input1i = mxGetImagData(prhs[0]);
/*figure out dimension info and number of elements*/
dims = mxGetDimensions(prhs[0]);
numdims = mxGetNumberOfDimensions(prhs[0]);
numelin = mxGetNumberOfElements(prhs[0]);
dimsout = mxMalloc(numdims * sizeof(mwSize));
for (i=0; i<numdims; i++)
{
dimsout[i] = dims[i];
}
dimsout[0] = 1;
dimsout[1] = 1;
/*associate output*/
if (input1i == NULL)
{
plhs[0] = mxCreateNumericArray(numdims, dimsout, classid, mxREAL);
output1r = mxGetData(plhs[0]);
}
else
{
plhs[0] = mxCreateNumericArray(numdims, dimsout, classid, mxCOMPLEX);
output1r = mxGetData(plhs[0]);
output1i = mxGetImagData(plhs[0]);
}
/* do the computation*/
if (input1i == NULL)
{
for (i=0; i<numelin/4; i++)
{
a = input1r[i*4 ];
b = input1r[i*4+1];
c = input1r[i*4+2];
d = input1r[i*4+3];
output1r[i] = a*d - b*c;
}
return;
}
else
{
for (i=0; i<numelin/4; i++)
{
/*matrix 1*/
a = input1r[i*4 ]; b = input1r[i*4+1]; c = input1r[i*4+2]; d = input1r[i*4+3];
ai = input1i[i*4 ]; bi = input1i[i*4+1]; ci = input1i[i*4+2]; di = input1i[i*4+3];
/*fill in the real part of the output matrix*/
output1r[i] = (a*d-ai*di) - (b*c-bi*ci);
/*fill in the imaginary part of the output matrix*/
output1i[i] = (ai*d+a*di) - (bi*c+b*ci);
}
return;
}
}

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