text: /* zlangt.f -- translated by f2c (version 20061008).
     You must link the resulting object file with libf2c:
  	on Microsoft Windows system, link with libf2c.lib;
  	on Linux or Unix systems, link with .../path/to/libf2c.a -lm
  	or, if you install libf2c.a in a standard place, with -lf2c -lm
  	-- in that order, at the end of the command line, as in
  		cc *.o -lf2c -lm
  	Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
  
  		http://www.netlib.org/f2c/libf2c.zip
  */
  
  #include "f2c.h"
  #include "blaswrap.h"
  
  /* Table of constant values */
  
  static integer c__1 = 1;
  
  doublereal zlangt_(char *norm, integer *n, doublecomplex *dl, doublecomplex *
  	d__, doublecomplex *du)
  {
      /* System generated locals */
      integer i__1;
      doublereal ret_val, d__1, d__2;
  
      /* Builtin functions */
      double z_abs(doublecomplex *), sqrt(doublereal);
  
      /* Local variables */
      integer i__;
      doublereal sum, scale;
      extern logical lsame_(char *, char *);
      doublereal anorm;
      extern /* Subroutine */ int zlassq_(integer *, doublecomplex *, integer *, 
  	     doublereal *, doublereal *);
  
  
  /*  -- LAPACK auxiliary routine (version 3.2) -- */
  /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
  /*     November 2006 */
  
  /*     .. Scalar Arguments .. */
  /*     .. */
  /*     .. Array Arguments .. */
  /*     .. */
  
  /*  Purpose */
  /*  ======= */
  
  /*  ZLANGT  returns the value of the one norm,  or the Frobenius norm, or */
  /*  the  infinity norm,  or the  element of  largest absolute value  of a */
  /*  complex tridiagonal matrix A. */
  
  /*  Description */
  /*  =========== */
  
  /*  ZLANGT returns the value */
  
  /*     ZLANGT = ( max(abs(A(i,j))), NORM = 'M' or 'm' */
  /*              ( */
  /*              ( norm1(A),         NORM = '1', 'O' or 'o' */
  /*              ( */
  /*              ( normI(A),         NORM = 'I' or 'i' */
  /*              ( */
  /*              ( normF(A),         NORM = 'F', 'f', 'E' or 'e' */
  
  /*  where  norm1  denotes the  one norm of a matrix (maximum column sum), */
  /*  normI  denotes the  infinity norm  of a matrix  (maximum row sum) and */
  /*  normF  denotes the  Frobenius norm of a matrix (square root of sum of */
  /*  squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm. */
  
  /*  Arguments */
  /*  ========= */
  
  /*  NORM    (input) CHARACTER*1 */
  /*          Specifies the value to be returned in ZLANGT as described */
  /*          above. */
  
  /*  N       (input) INTEGER */
  /*          The order of the matrix A.  N >= 0.  When N = 0, ZLANGT is */
  /*          set to zero. */
  
  /*  DL      (input) COMPLEX*16 array, dimension (N-1) */
  /*          The (n-1) sub-diagonal elements of A. */
  
  /*  D       (input) COMPLEX*16 array, dimension (N) */
  /*          The diagonal elements of A. */
  
  /*  DU      (input) COMPLEX*16 array, dimension (N-1) */
  /*          The (n-1) super-diagonal elements of A. */
  
  /*  ===================================================================== */
  
  /*     .. Parameters .. */
  /*     .. */
  /*     .. Local Scalars .. */
  /*     .. */
  /*     .. External Functions .. */
  /*     .. */
  /*     .. External Subroutines .. */
  /*     .. */
  /*     .. Intrinsic Functions .. */
  /*     .. */
  /*     .. Executable Statements .. */
  
      /* Parameter adjustments */
      --du;
      --d__;
      --dl;
  
      /* Function Body */
      if (*n <= 0) {
  	anorm = 0.;
      } else if (lsame_(norm, "M")) {
  
  /*        Find max(abs(A(i,j))). */
  
  	anorm = z_abs(&d__[*n]);
  	i__1 = *n - 1;
  	for (i__ = 1; i__ <= i__1; ++i__) {
  /* Computing MAX */
  	    d__1 = anorm, d__2 = z_abs(&dl[i__]);
  	    anorm = max(d__1,d__2);
  /* Computing MAX */
  	    d__1 = anorm, d__2 = z_abs(&d__[i__]);
  	    anorm = max(d__1,d__2);
  /* Computing MAX */
  	    d__1 = anorm, d__2 = z_abs(&du[i__]);
  	    anorm = max(d__1,d__2);
  /* L10: */
  	}
      } else if (lsame_(norm, "O") || *(unsigned char *)
  	    norm == '1') {
  
  /*        Find norm1(A). */
  
  	if (*n == 1) {
  	    anorm = z_abs(&d__[1]);
  	} else {
  /* Computing MAX */
  	    d__1 = z_abs(&d__[1]) + z_abs(&dl[1]), d__2 = z_abs(&d__[*n]) + 
  		    z_abs(&du[*n - 1]);
  	    anorm = max(d__1,d__2);
  	    i__1 = *n - 1;
  	    for (i__ = 2; i__ <= i__1; ++i__) {
  /* Computing MAX */
  		d__1 = anorm, d__2 = z_abs(&d__[i__]) + z_abs(&dl[i__]) + 
  			z_abs(&du[i__ - 1]);
  		anorm = max(d__1,d__2);
  /* L20: */
  	    }
  	}
      } else if (lsame_(norm, "I")) {
  
  /*        Find normI(A). */
  
  	if (*n == 1) {
  	    anorm = z_abs(&d__[1]);
  	} else {
  /* Computing MAX */
  	    d__1 = z_abs(&d__[1]) + z_abs(&du[1]), d__2 = z_abs(&d__[*n]) + 
  		    z_abs(&dl[*n - 1]);
  	    anorm = max(d__1,d__2);
  	    i__1 = *n - 1;
  	    for (i__ = 2; i__ <= i__1; ++i__) {
  /* Computing MAX */
  		d__1 = anorm, d__2 = z_abs(&d__[i__]) + z_abs(&du[i__]) + 
  			z_abs(&dl[i__ - 1]);
  		anorm = max(d__1,d__2);
  /* L30: */
  	    }
  	}
      } else if (lsame_(norm, "F") || lsame_(norm, "E")) {
  
  /*        Find normF(A). */
  
  	scale = 0.;
  	sum = 1.;
  	zlassq_(n, &d__[1], &c__1, &scale, &sum);
  	if (*n > 1) {
  	    i__1 = *n - 1;
  	    zlassq_(&i__1, &dl[1], &c__1, &scale, &sum);
  	    i__1 = *n - 1;
  	    zlassq_(&i__1, &du[1], &c__1, &scale, &sum);
  	}
  	anorm = scale * sqrt(sum);
      }
  
      ret_val = anorm;
      return ret_val;
  
  /*     End of ZLANGT */
  
  } /* zlangt_ */
  