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

6       SGTTRS - one of the systems of equations  A*X = B or A'*X = B,
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SYNOPSIS

9       SUBROUTINE SGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )
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11           CHARACTER      TRANS
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13           INTEGER        INFO, LDB, N, NRHS
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15           INTEGER        IPIV( * )
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17           REAL           B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )
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PURPOSE

20       SGTTRS solves one of the systems of equations
21          A*X = B  or  A'*X = B, with a tridiagonal matrix A using the LU fac‐
22       torization computed by SGTTRF.
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ARGUMENTS

26       TRANS   (input) CHARACTER*1
27               Specifies the form of the system of equations.  = 'N':  A * X =
28               B  (No transpose)
29               = 'T':  A'* X = B  (Transpose)
30               = 'C':  A'* X = B  (Conjugate transpose = Transpose)
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32       N       (input) INTEGER
33               The order of the matrix A.
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35       NRHS    (input) INTEGER
36               The  number of right hand sides, i.e., the number of columns of
37               the matrix B.  NRHS >= 0.
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39       DL      (input) REAL array, dimension (N-1)
40               The (n-1) multipliers that define the matrix L from the LU fac‐
41               torization of A.
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43       D       (input) REAL array, dimension (N)
44               The  n  diagonal elements of the upper triangular matrix U from
45               the LU factorization of A.
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47       DU      (input) REAL array, dimension (N-1)
48               The (n-1) elements of the first super-diagonal of U.
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50       DU2     (input) REAL array, dimension (N-2)
51               The (n-2) elements of the second super-diagonal of U.
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53       IPIV    (input) INTEGER array, dimension (N)
54               The pivot indices; for 1 <= i <= n, row i  of  the  matrix  was
55               interchanged with row IPIV(i).  IPIV(i) will always be either i
56               or i+1; IPIV(i)  =  i  indicates  a  row  interchange  was  not
57               required.
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59       B       (input/output) REAL array, dimension (LDB,NRHS)
60               On  entry, the matrix of right hand side vectors B.  On exit, B
61               is overwritten by the solution vectors X.
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63       LDB     (input) INTEGER
64               The leading dimension of the array B.  LDB >= max(1,N).
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66       INFO    (output) INTEGER
67               = 0:  successful exit
68               < 0:  if INFO = -i, the i-th argument had an illegal value
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72 LAPACK routine (version 3.1)    November 2006                       SGTTRS(1)
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