LAPACK 3.12.0 LAPACK: Linear Algebra PACKage
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◆ cptsv()

 subroutine cptsv ( integer n, integer nrhs, real, dimension( * ) d, complex, dimension( * ) e, complex, dimension( ldb, * ) b, integer ldb, integer info )

CPTSV computes the solution to system of linear equations A * X = B for PT matrices

Purpose:
``` CPTSV computes the solution to a complex system of linear equations
A*X = B, where A is an N-by-N Hermitian positive definite tridiagonal
matrix, and X and B are N-by-NRHS matrices.

A is factored as A = L*D*L**H, and the factored form of A is then
used to solve the system of equations.```
Parameters
 [in] N ``` N is INTEGER The order of the matrix A. N >= 0.``` [in] NRHS ``` NRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.``` [in,out] D ``` D is REAL array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, the n diagonal elements of the diagonal matrix D from the factorization A = L*D*L**H.``` [in,out] E ``` E is COMPLEX array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A. On exit, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**H factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the U**H*D*U factorization of A.``` [in,out] B ``` B is COMPLEX 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.``` [in] LDB ``` LDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).``` [out] INFO ``` INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, the leading principal minor of order i is not positive, and the solution has not been computed. The factorization has not been completed unless i = N.```

Definition at line 114 of file cptsv.f.

115*
116* -- LAPACK driver routine --
117* -- LAPACK is a software package provided by Univ. of Tennessee, --
118* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
119*
120* .. Scalar Arguments ..
121 INTEGER INFO, LDB, N, NRHS
122* ..
123* .. Array Arguments ..
124 REAL D( * )
125 COMPLEX B( LDB, * ), E( * )
126* ..
127*
128* =====================================================================
129*
130* .. External Subroutines ..
131 EXTERNAL cpttrf, cpttrs, xerbla
132* ..
133* .. Intrinsic Functions ..
134 INTRINSIC max
135* ..
136* .. Executable Statements ..
137*
138* Test the input parameters.
139*
140 info = 0
141 IF( n.LT.0 ) THEN
142 info = -1
143 ELSE IF( nrhs.LT.0 ) THEN
144 info = -2
145 ELSE IF( ldb.LT.max( 1, n ) ) THEN
146 info = -6
147 END IF
148 IF( info.NE.0 ) THEN
149 CALL xerbla( 'CPTSV ', -info )
150 RETURN
151 END IF
152*
153* Compute the L*D*L**H (or U**H*D*U) factorization of A.
154*
155 CALL cpttrf( n, d, e, info )
156 IF( info.EQ.0 ) THEN
157*
158* Solve the system A*X = B, overwriting B with X.
159*
160 CALL cpttrs( 'Lower', n, nrhs, d, e, b, ldb, info )
161 END IF
162 RETURN
163*
164* End of CPTSV
165*
subroutine xerbla(srname, info)
Definition cblat2.f:3285
subroutine cpttrf(n, d, e, info)
CPTTRF
Definition cpttrf.f:92
subroutine cpttrs(uplo, n, nrhs, d, e, b, ldb, info)
CPTTRS
Definition cpttrs.f:121
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