#include "blaswrap.h" #include "f2c.h" doublereal dlanhs_(char *norm, integer *n, doublereal *a, integer *lda, doublereal *work) { /* -- LAPACK auxiliary routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= DLANHS returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a Hessenberg matrix A. Description =========== DLANHS returns the value DLANHS = ( 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 DLANHS as described above. N (input) INTEGER The order of the matrix A. N >= 0. When N = 0, DLANHS is set to zero. A (input) DOUBLE PRECISION array, dimension (LDA,N) The n by n upper Hessenberg matrix A; the part of A below the first sub-diagonal is not referenced. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(N,1). WORK (workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK)), where LWORK >= N when NORM = 'I'; otherwise, WORK is not referenced. ===================================================================== Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; /* System generated locals */ integer a_dim1, a_offset, i__1, i__2, i__3, i__4; doublereal ret_val, d__1, d__2, d__3; /* Builtin functions */ double sqrt(doublereal); /* Local variables */ static integer i__, j; static doublereal sum, scale; extern logical lsame_(char *, char *); static doublereal value; extern /* Subroutine */ int dlassq_(integer *, doublereal *, integer *, doublereal *, doublereal *); a_dim1 = *lda; a_offset = 1 + a_dim1; a -= a_offset; --work; /* Function Body */ if (*n == 0) { value = 0.; } else if (lsame_(norm, "M")) { /* Find max(abs(A(i,j))). */ value = 0.; i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MIN */ i__3 = *n, i__4 = j + 1; i__2 = min(i__3,i__4); for (i__ = 1; i__ <= i__2; ++i__) { /* Computing MAX */ d__2 = value, d__3 = (d__1 = a[i__ + j * a_dim1], abs(d__1)); value = max(d__2,d__3); /* L10: */ } /* L20: */ } } else if (lsame_(norm, "O") || *(unsigned char *) norm == '1') { /* Find norm1(A). */ value = 0.; i__1 = *n; for (j = 1; j <= i__1; ++j) { sum = 0.; /* Computing MIN */ i__3 = *n, i__4 = j + 1; i__2 = min(i__3,i__4); for (i__ = 1; i__ <= i__2; ++i__) { sum += (d__1 = a[i__ + j * a_dim1], abs(d__1)); /* L30: */ } value = max(value,sum); /* L40: */ } } else if (lsame_(norm, "I")) { /* Find normI(A). */ i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { work[i__] = 0.; /* L50: */ } i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MIN */ i__3 = *n, i__4 = j + 1; i__2 = min(i__3,i__4); for (i__ = 1; i__ <= i__2; ++i__) { work[i__] += (d__1 = a[i__ + j * a_dim1], abs(d__1)); /* L60: */ } /* L70: */ } value = 0.; i__1 = *n; for (i__ = 1; i__ <= i__1; ++i__) { /* Computing MAX */ d__1 = value, d__2 = work[i__]; value = max(d__1,d__2); /* L80: */ } } else if (lsame_(norm, "F") || lsame_(norm, "E")) { /* Find normF(A). */ scale = 0.; sum = 1.; i__1 = *n; for (j = 1; j <= i__1; ++j) { /* Computing MIN */ i__3 = *n, i__4 = j + 1; i__2 = min(i__3,i__4); dlassq_(&i__2, &a[j * a_dim1 + 1], &c__1, &scale, &sum); /* L90: */ } value = scale * sqrt(sum); } ret_val = value; return ret_val; /* End of DLANHS */ } /* dlanhs_ */