HP MLIB User's Guide Vol. 1 7th Ed.

300 HP MLIB User’s Guide
STBMV/DTBMV/CTBMV/ZTBMV Matrix-vector multiply
Error conditions are
uplo ≠ ’L’ or ’l’ or ’U’ or ’u’
trans ≠ ’N’ or ’n’ or ’T’ or ’t’ or ’C’ or ’c’
diag ≠ ’N’ or ’n’ or ’U’ or ’u’
n < 0
kd < 0
ldab < kd+1
incx = 0
Actual character arguments in a subroutine call can be longer than the
corresponding dummy arguments. Therefore, readability of the CALL
statement can be improved by coding the trans argument as ’NORMAL’ or
’NONTRANS’ for ’N’, ’TRANSPOSE’ for ’T’, or ’CTRANS’ for ’C’. Refer to
“Example 2.”
Example 1 Form the REAL*4 matrix-vector product Ax, where A is a 75-by-75
unit-diagonal, lower-triangular real band matrix with bandwidth 15 that is
stored in an array AB whose dimensions are 25-by-100, and x is a real vector 75
elements long stored in an array X of dimension 100.
CHARACTER*1 UPLO,TRANS,DIAG
INTEGER*4 N,KD,LDAB,INCX
REAL*4 AB(25,100),X(100)
UPLO = ’L’
TRANS = ’N’
DIAG = ’U’
N = 75
KD = 15
LDAB = 25
INCX = 1
CALL STBMV (UPLO,TRANS,DIAG,N,KD,AB,LDAB,X,INCX)
Example 2 Form the REAL*8 matrix-vector product A
T
x, where A is a 75-by-75
nonunit-diagonal, upper-triangular real band matrix with bandwidth 15 that is
stored in an array AB whose dimensions are 25-by-100, and x is a real vector 75
elements long stored in an array X of dimension 100.
INTEGER*4 N,KD,LDAB
REAL*4 AB(25,100),X(100)
N = 75
KD = 15
LDAB = 25
CALL DTBMV (’UPPER’,’TRANSPOSE’,’NONUNIT’,N,KD,AB,LDAB,X,1)