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

312 HP MLIB User’s Guide
STPMV/DTPMV/CTPMV/ZTPMV Matrix-vector multiply
Notes These subprograms conform to specifications of the Level 2 BLAS.
If an error in the arguments is detected, the subprograms call error handler
XERBLA, which writes an error message onto the standard error file and
terminates execution. The standard version of XERBLA (refer to the end of this
chapter) can be replaced with a user-supplied version to change the error
procedure. 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
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 9-by-9 unit-diagonal,
lower-triangular real matrix stored in packed form in an array AP of dimension
55 and x is a real vector 9 elements long stored in an array X of dimension 10.
CHARACTER*1 UPLO,TRANS,DIAG
INTEGER*4 N,INCX
REAL*4 AP(55),X(10)
UPLO = ’L’
TRANS = ’N’
DIAG = ’U’
N = 9
INCX = 1
CALL STPMV (UPLO,TRANS,DIAG,N,AP,X,INCX)
Example 2 Form the REAL*8 matrix-vector product A
T
x, where A is a 9-by-9
nonunit-diagonal, upper-triangular real matrix stored in packed form in an
array AP of dimension 55 and x is a real vector 9 elements long stored in an
array X of dimension 10.
INTEGER*4 N
REAL*8 AP(55),X(10)
N = 6
CALL DTPMV (’UPPER’,’TRANSPOSE’,’NONUNIT’,N,AP,X,1)