/* 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. * * * */ mtransp( n, A, T ) int n; double *A, *T; { int i, j, np1; double *pAc, *pAr, *pTc, *pTr, *pA0, *pT0; double x, y; 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 */ }