/*! @file dzsum1.c

 * \brief Takes sum of the absolute values of a complex vector and returns a double precision result

 *

 * 

 *     -- LAPACK auxiliary routine (version 2.0) --   

 *     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   

 *     Courant Institute, Argonne National Lab, and Rice University   

 *     October 31, 1992   

 * 

 */

#include "slu_dcomplex.h"

#include "slu_Cnames.h"

/*! \brief

    Purpose   

    =======   

    DZSUM1 takes the sum of the absolute values of a complex   

    vector and returns a double precision result.   

    Based on DZASUM from the Level 1 BLAS.   

    The change is to use the 'genuine' absolute value.   

    Contributed by Nick Higham for use with ZLACON.   

    Arguments   

    =========   

    N       (input) INT   

            The number of elements in the vector CX.   

    CX      (input) COMPLEX*16 array, dimension (N)   

            The vector whose elements will be summed.   

    INCX    (input) INT   

            The spacing between successive values of CX.  INCX > 0.   

    ===================================================================== 

*/  

double dzsum1_(int *n, doublecomplex *cx, int *incx)

{

    /* Builtin functions */

    double z_abs(doublecomplex *);

    /* Local variables */

    int i, nincx;

    double stemp;

#define CX(I) cx[(I)-1]

    stemp = 0.;

    if (*n <= 0) {

	return stemp;

    }

    if (*incx == 1) {

	goto L20;

    }

    /*     CODE FOR INCREMENT NOT EQUAL TO 1 */

    nincx = *n * *incx;

    for (i = 1; *incx < 0 ? i >= nincx : i <= nincx; i += *incx) {

	/*        NEXT LINE MODIFIED. */

	stemp += z_abs(&CX(i));

/* L10: */

    }

    return stemp;

    /*     CODE FOR INCREMENT EQUAL TO 1 */

L20:

    for (i = 1; i <= *n; ++i) {

	/*        NEXT LINE MODIFIED. */

	stemp += z_abs(&CX(i));

/* L30: */

    }

    return stemp;

    /*     End of DZSUM1 */

} /* dzsum1_ */