*DECK DSOSSL
SUBROUTINE DSOSSL (K, N, L, X, C, B, M)
C***BEGIN PROLOGUE DSOSSL
C***SUBSIDIARY
C***PURPOSE Subsidiary to DSOS
C***LIBRARY SLATEC
C***TYPE DOUBLE PRECISION (SOSSOL-S, DSOSSL-D)
C***AUTHOR (UNKNOWN)
C***DESCRIPTION
C
C DSOSSL solves an upper triangular type of linear system by back
C substitution.
C
C The matrix C is upper trapezoidal and stored as a linear array by
C rows. The equations have been normalized so that the diagonal
C entries of C are understood to be unity. The off diagonal entries
C and the elements of the constant right hand side vector B have
C already been stored as the negatives of the corresponding equation
C values.
C With each call to DSOSSL a (K-1) by (K-1) triangular system is
C resolved. For L greater than K, column L of C is included in the
C right hand side vector.
C
C***SEE ALSO DSOS
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 801001 DATE WRITTEN
C 890831 Modified array declarations. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900328 Added TYPE section. (WRB)
C***END PROLOGUE DSOSSL
C
C
INTEGER J, JKM, K, KJ, KM, KM1, KMM1, KN, L, LK, M, N, NP1
DOUBLE PRECISION B(*), C(*), X(*), XMAX
C
C***FIRST EXECUTABLE STATEMENT DSOSSL
NP1 = N + 1
KM1 = K - 1
LK = KM1
IF (L .EQ. K) LK = K
KN = M
C
C
DO 40 KJ = 1, KM1
KMM1 = K - KJ
KM = KMM1 + 1
XMAX = 0.0D0
KN = KN - NP1 + KMM1
IF (KM .GT. LK) GO TO 20
JKM = KN
C
DO 10 J = KM, LK
JKM = JKM + 1
XMAX = XMAX + C(JKM)*X(J)
10 CONTINUE
20 CONTINUE
C
IF (L .LE. K) GO TO 30
JKM = KN + L - KMM1
XMAX = XMAX + C(JKM)*X(L)
30 CONTINUE
X(KMM1) = XMAX + B(KMM1)
40 CONTINUE
C
RETURN
END