Previous: slanst Up: ../lapack-s.html Next: slantb

NAME SLANSY - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest abso- lute value of a real symmetric matrix A SYNOPSIS REAL FUNCTION SLANSY( NORM, UPLO, N, A, LDA, WORK ) CHARACTER NORM, UPLO INTEGER LDA, N REAL A( LDA, * ), WORK( * ) PURPOSE SLANSY returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric matrix A. DESCRIPTION SLANSY returns the value SLANSY = ( 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 SLANSY as described above. UPLO (input) CHARACTER*1 Specifies whether the upper or lower triangular part of the symmetric matrix A is to be referenced. = 'U': Upper triangular part of A is referenced = 'L': Lower triangular part of A is referenced N (input) INTEGER The order of the matrix A. N >= 0. When N = 0, SLANSY is set to zero. A (input) REAL array, dimension (LDA,N) The symmetric matrix A. If UPLO = 'U', the leading n by n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading n by n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(N,1). WORK (workspace) REAL array, dimension (LWORK), where LWORK >= N when NORM = 'I' or '1' or 'O'; oth- erwise, WORK is not referenced.