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

NAME SLANTP - 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 triangular matrix A, supplied in packed form SYNOPSIS REAL FUNCTION SLANTP( NORM, UPLO, DIAG, N, AP, WORK ) CHARACTER DIAG, NORM, UPLO INTEGER N REAL AP( * ), WORK( * ) PURPOSE SLANTP returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a triangular matrix A, supplied in packed form. DESCRIPTION SLANTP returns the value SLANTP = ( 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 SLANTP as described above. UPLO (input) CHARACTER*1 Specifies whether the matrix A is upper or lower triangular. = 'U': Upper triangular = 'L': Lower triangular DIAG (input) CHARACTER*1 Specifies whether or not the matrix A is unit tri- angular. = 'N': Non-unit triangular = 'U': Unit triangular N (input) INTEGER The order of the matrix A. N >= 0. When N = 0, SLANTP is set to zero. AP (input) REAL array, dimension (N*(N+1)/2) The upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. Note that when DIAG = 'U', the elements of the array AP corresponding to the diagonal elements of the matrix A are not referenced, but are assumed to be one. WORK (workspace) REAL array, dimension (LWORK), where LWORK >= N when NORM = 'I'; otherwise, WORK is not referenced.