# sspsl.f

```      SUBROUTINE SSPSL (AP, N, KPVT, B)
C***BEGIN PROLOGUE  SSPSL
C***PURPOSE  Solve a real symmetric system using the factors obtained
C            from SSPFA.
C***LIBRARY   SLATEC (LINPACK)
C***CATEGORY  D2B1A
C***TYPE      SINGLE PRECISION (SSPSL-S, DSPSL-D, CHPSL-C, CSPSL-C)
C***KEYWORDS  LINEAR ALGEBRA, LINPACK, MATRIX, PACKED, SOLVE, SYMMETRIC
C***AUTHOR  Bunch, J., (UCSD)
C***DESCRIPTION
C
C     SSISL solves the real symmetric system
C     A * X = B
C     using the factors computed by SSPFA.
C
C     On Entry
C
C        AP      REAL(N*(N+1)/2)
C                the output from SSPFA.
C
C        N       INTEGER
C                the order of the matrix  A .
C
C        KPVT    INTEGER(N)
C                the pivot vector from SSPFA.
C
C        B       REAL(N)
C                the right hand side vector.
C
C     On Return
C
C        B       the solution vector  X .
C
C     Error Condition
C
C        A division by zero may occur if  SSPCO  has set RCOND .EQ. 0.0
C        or  SSPFA  has set INFO .NE. 0  .
C
C     To compute  INVERSE(A) * C  where  C  is a matrix
C     with  P  columns
C           CALL SSPFA(AP,N,KPVT,INFO)
C           IF (INFO .NE. 0) GO TO ...
C           DO 10 J = 1, P
C              CALL SSPSL(AP,N,KPVT,C(1,J))
C        10 CONTINUE
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   890531  Changed all specific intrinsics to generic.  (WRB)
C   890831  Modified array declarations.  (WRB)
C   891107  Modified routine equivalence list.  (WRB)
C   891107  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  SSPSL
```