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NAME CLANSB - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest abso- lute value of an n by n symmetric band matrix A, with k super-diagonals SYNOPSIS REAL FUNCTION CLANSB( NORM, UPLO, N, K, AB, LDAB, WORK ) CHARACTER NORM, UPLO INTEGER K, LDAB, N REAL WORK( * ) COMPLEX AB( LDAB, * ) PURPOSE CLANSB returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of an n by n symmetric band matrix A, with k super-diagonals. DESCRIPTION CLANSB returns the value CLANSB = ( 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 matrix norm. ARGUMENTS NORM (input) CHARACTER*1 Specifies the value to be returned in CLANSB as described above. UPLO (input) CHARACTER*1 Specifies whether the upper or lower triangular part of the band matrix A is supplied. = 'U': Upper triangular part is supplied = 'L': Lower triangular part is supplied N (input) INTEGER The order of the matrix A. N >= 0. When N = 0, CLANSB is set to zero. K (input) INTEGER The number of super-diagonals or sub-diagonals of the band matrix A. K >= 0. AB (input) COMPLEX array, dimension (LDAB,N) The upper or lower triangle of the symmetric band matrix A, stored in the first K+1 rows of AB. The j-th column of A is stored in the j-th column of the array AB as follows: if UPLO = 'U', AB(k+1+i-j,j) = A(i,j) for max(1,j-k)<=i<=j; if UPLO = 'L', AB(1+i- j,j) = A(i,j) for j<=i<=min(n,j+k). LDAB (input) INTEGER The leading dimension of the array AB. LDAB >= K+1. WORK (workspace) REAL array, dimension (LWORK), where LWORK >= N when NORM = 'I' or '1' or 'O'; oth- erwise, WORK is not referenced.