3 /* Table of constant values */
5 static integer c__1 = 1;
7 doublereal slanst_(char *norm, integer *n, real *d__, real *e)
9 /* System generated locals */
11 real ret_val, r__1, r__2, r__3, r__4, r__5;
13 /* Builtin functions */
14 double sqrt(doublereal);
19 extern logical lsame_(char *, char *);
21 extern /* Subroutine */ int slassq_(integer *, real *, integer *, real *,
25 /* -- LAPACK auxiliary routine (version 3.1) -- */
26 /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
29 /* .. Scalar Arguments .. */
31 /* .. Array Arguments .. */
37 /* SLANST returns the value of the one norm, or the Frobenius norm, or */
38 /* the infinity norm, or the element of largest absolute value of a */
39 /* real symmetric tridiagonal matrix A. */
44 /* SLANST returns the value */
46 /* SLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm' */
48 /* ( norm1(A), NORM = '1', 'O' or 'o' */
50 /* ( normI(A), NORM = 'I' or 'i' */
52 /* ( normF(A), NORM = 'F', 'f', 'E' or 'e' */
54 /* where norm1 denotes the one norm of a matrix (maximum column sum), */
55 /* normI denotes the infinity norm of a matrix (maximum row sum) and */
56 /* normF denotes the Frobenius norm of a matrix (square root of sum of */
57 /* squares). Note that max(abs(A(i,j))) is not a consistent matrix norm. */
62 /* NORM (input) CHARACTER*1 */
63 /* Specifies the value to be returned in SLANST as described */
66 /* N (input) INTEGER */
67 /* The order of the matrix A. N >= 0. When N = 0, SLANST is */
70 /* D (input) REAL array, dimension (N) */
71 /* The diagonal elements of A. */
73 /* E (input) REAL array, dimension (N-1) */
74 /* The (n-1) sub-diagonal or super-diagonal elements of A. */
76 /* ===================================================================== */
78 /* .. Parameters .. */
80 /* .. Local Scalars .. */
82 /* .. External Functions .. */
84 /* .. External Subroutines .. */
86 /* .. Intrinsic Functions .. */
88 /* .. Executable Statements .. */
90 /* Parameter adjustments */
97 } else if (lsame_(norm, "M")) {
99 /* Find max(abs(A(i,j))). */
101 anorm = (r__1 = d__[*n], dabs(r__1));
103 for (i__ = 1; i__ <= i__1; ++i__) {
105 r__2 = anorm, r__3 = (r__1 = d__[i__], dabs(r__1));
106 anorm = dmax(r__2,r__3);
108 r__2 = anorm, r__3 = (r__1 = e[i__], dabs(r__1));
109 anorm = dmax(r__2,r__3);
112 } else if (lsame_(norm, "O") || *(unsigned char *)
113 norm == '1' || lsame_(norm, "I")) {
118 anorm = dabs(d__[1]);
121 r__3 = dabs(d__[1]) + dabs(e[1]), r__4 = (r__1 = e[*n - 1], dabs(
122 r__1)) + (r__2 = d__[*n], dabs(r__2));
123 anorm = dmax(r__3,r__4);
125 for (i__ = 2; i__ <= i__1; ++i__) {
127 r__4 = anorm, r__5 = (r__1 = d__[i__], dabs(r__1)) + (r__2 =
128 e[i__], dabs(r__2)) + (r__3 = e[i__ - 1], dabs(r__3));
129 anorm = dmax(r__4,r__5);
133 } else if (lsame_(norm, "F") || lsame_(norm, "E")) {
141 slassq_(&i__1, &e[1], &c__1, &scale, &sum);
144 slassq_(n, &d__[1], &c__1, &scale, &sum);
145 anorm = scale * sqrt(sum);