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

Chapter 3 Basic Matrix Operations 307
Solve triangular band system STBSV/DTBSV/CTBSV/ZTBSV
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 may 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 Perform REAL*4 forward elimination using the 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 STBSV (UPLO,TRANS,DIAG,N,KD,AB,LDAB,X,INCX)
Example 2 Perform REAL*4 back substitution using the 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 STBSV (’UPPER’,’NONTRANS’,’NONUNIT’,N,KD,AB,LDAB,X,1)