strsl.f
SUBROUTINE STRSL (T, LDT, N, B, JOB, INFO)
C***BEGIN PROLOGUE STRSL
C***PURPOSE Solve a system of the form T*X=B or TRANS(T)*X=B, where
C T is a triangular matrix.
C***LIBRARY SLATEC (LINPACK)
C***CATEGORY D2A3
C***TYPE SINGLE PRECISION (STRSL-S, DTRSL-D, CTRSL-C)
C***KEYWORDS LINEAR ALGEBRA, LINPACK, TRIANGULAR LINEAR SYSTEM,
C TRIANGULAR MATRIX
C***AUTHOR Stewart, G. W., (U. of Maryland)
C***DESCRIPTION
C
C STRSL solves systems of the form
C
C T * X = B
C or
C TRANS(T) * X = B
C
C where T is a triangular matrix of order N. Here TRANS(T)
C denotes the transpose of the matrix T.
C
C On Entry
C
C T REAL(LDT,N)
C T contains the matrix of the system. The zero
C elements of the matrix are not referenced, and
C the corresponding elements of the array can be
C used to store other information.
C
C LDT INTEGER
C LDT is the leading dimension of the array T.
C
C N INTEGER
C N is the order of the system.
C
C B REAL(N).
C B contains the right hand side of the system.
C
C JOB INTEGER
C JOB specifies what kind of system is to be solved.
C If JOB is
C
C 00 solve T*X=B, T lower triangular,
C 01 solve T*X=B, T upper triangular,
C 10 solve TRANS(T)*X=B, T lower triangular,
C 11 solve TRANS(T)*X=B, T upper triangular.
C
C On Return
C
C B B contains the solution, if INFO .EQ. 0.
C Otherwise B is unaltered.
C
C INFO INTEGER
C INFO contains zero if the system is nonsingular.
C Otherwise INFO contains the index of
C the first zero diagonal element of T.
C
C***REFERENCES J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W.
C Stewart, LINPACK Users' Guide, SIAM, 1979.
C***ROUTINES CALLED SAXPY, SDOT
C***REVISION HISTORY (YYMMDD)
C 780814 DATE WRITTEN
C 890831 Modified array declarations. (WRB)
C 890831 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE STRSL