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/* mtransp.c
*
* Matrix transpose
*
*
*
* SYNOPSIS:
*
* int n;
* double A[n*n], T[n*n];
*
* mtransp( n, A, T );
*
*
*
* DESCRIPTION:
*
*
* T[r][c] = A[c][r]
*
*
* Transposes the n by n square matrix A and puts the result in T.
* The output, T, may occupy the same storage as A.
*
*
*
*/
void mtransp( int,double*,double* );
void
mtransp( n, A, T )
int n;
double *A, *T;
{
int i, j, np1;
double *pAc, *pAr, *pTc, *pTr, *pA0, *pT0;
double x;
np1 = n+1;
pA0 = A;
pT0 = T;
for( i=0; i<n-1; i++ ) /* row index */
{
pAc = pA0; /* next diagonal element of input */
pAr = pAc + n; /* next row down underneath the diagonal element */
pTc = pT0; /* next diagonal element of the output */
pTr = pTc + n; /* next row underneath */
*pTc++ = *pAc++; /* copy the diagonal element */
for( j=i+1; j<n; j++ ) /* column index */
{
x = *pAr;
*pTr = *pAc++;
*pTc++ = x;
pAr += n;
pTr += n;
}
pA0 += np1; /* &A[n*i+i] for next i */
pT0 += np1; /* &T[n*i+i] for next i */
}
*pT0 = *pA0; /* copy the diagonal element */
}
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