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- NNNNAAAAMMMMEEEE
- SGTSV - solve the equation A*X = B,
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- SUBROUTINE SGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )
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- INTEGER INFO, LDB, N, NRHS
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- REAL B( LDB, * ), D( * ), DL( * ), DU( * )
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- PPPPUUUURRRRPPPPOOOOSSSSEEEE
- SGTSV solves the equation
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- where A is an N-by-N tridiagonal matrix, by Gaussian elimination with
- partial pivoting.
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- Note that the equation A'*X = B may be solved by interchanging the
- order of the arguments DU and DL.
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- AAAARRRRGGGGUUUUMMMMEEEENNNNTTTTSSSS
- N (input) INTEGER
- The order of the matrix A. N >= 0.
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- NRHS (input) INTEGER
- The number of right hand sides, i.e., the number of columns of
- the matrix B. NRHS >= 0.
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- DL (input/output) REAL array, dimension (N-1)
- On entry, DL must contain the (n-1) subdiagonal elements of A.
- On exit, DL is overwritten by the (n-2) elements of the second
- superdiagonal of the upper triangular matrix U from the LU
- factorization of A, in DL(1), ..., DL(n-2).
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- D (input/output) REAL array, dimension (N)
- On entry, D must contain the diagonal elements of A. On exit, D
- is overwritten by the n diagonal elements of U.
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- DU (input/output) REAL array, dimension (N-1)
- On entry, DU must contain the (n-1) superdiagonal elements of A.
- On exit, DU is overwritten by the (n-1) elements of the first
- superdiagonal of U.
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- B (input/output) REAL array, dimension (LDB,NRHS)
- On entry, the N-by-NRHS right hand side matrix B. On exit, if
- INFO = 0, the N-by-NRHS solution matrix X.
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- LDB (input) INTEGER
- The leading dimension of the array B. LDB >= max(1,N).
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- PPPPaaaaggggeeee 1111
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- SSSSGGGGTTTTSSSSVVVV((((3333FFFF)))) SSSSGGGGTTTTSSSSVVVV((((3333FFFF))))
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- INFO (output) INTEGER
- = 0: successful exit
- < 0: if INFO = -i, the i-th argument had an illegal value
- > 0: if INFO = i, U(i,i) is exactly zero, and the solution has
- not been computed. The factorization has not been completed
- unless i = N.
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- PPPPaaaaggggeeee 2222
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