1SPTSV(1)                 LAPACK routine (version 3.1)                 SPTSV(1)
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NAME

6       SPTSV  -  the  solution  to  a real system of linear equations A*X = B,
7       where A is an N-by-N symmetric positive  definite  tridiagonal  matrix,
8       and X and B are N-by-NRHS matrices
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SYNOPSIS

11       SUBROUTINE SPTSV( N, NRHS, D, E, B, LDB, INFO )
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13           INTEGER       INFO, LDB, N, NRHS
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15           REAL          B( LDB, * ), D( * ), E( * )
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PURPOSE

18       SPTSV  computes the solution to a real system of linear equations A*X =
19       B, where A is an N-by-N symmetric positive definite tridiagonal matrix,
20       and X and B are N-by-NRHS matrices.
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22       A  is factored as A = L*D*L**T, and the factored form of A is then used
23       to solve the system of equations.
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ARGUMENTS

27       N       (input) INTEGER
28               The order of the matrix A.  N >= 0.
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30       NRHS    (input) INTEGER
31               The number of right hand sides, i.e., the number of columns  of
32               the matrix B.  NRHS >= 0.
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34       D       (input/output) REAL array, dimension (N)
35               On  entry, the n diagonal elements of the tridiagonal matrix A.
36               On exit, the n diagonal elements of the diagonal matrix D  from
37               the factorization A = L*D*L**T.
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39       E       (input/output) REAL array, dimension (N-1)
40               On  entry,  the  (n-1)  subdiagonal elements of the tridiagonal
41               matrix A.  On exit, the (n-1) subdiagonal elements of the  unit
42               bidiagonal  factor  L from the L*D*L**T factorization of A.  (E
43               can also be regarded as the superdiagonal of the unit  bidiago‐
44               nal factor U from the U**T*D*U factorization of A.)
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46       B       (input/output) REAL array, dimension (LDB,NRHS)
47               On  entry, the N-by-NRHS right hand side matrix B.  On exit, if
48               INFO = 0, the N-by-NRHS solution matrix X.
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50       LDB     (input) INTEGER
51               The leading dimension of the array B.  LDB >= max(1,N).
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53       INFO    (output) INTEGER
54               = 0:  successful exit
55               < 0:  if INFO = -i, the i-th argument had an illegal value
56               > 0:  if INFO = i, the leading minor of order i is not positive
57               definite,  and the solution has not been computed.  The factor‐
58               ization has not been completed unless i = N.
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62 LAPACK routine (version 3.1)    November 2006                        SPTSV(1)