Annotation of rpl/lapack/lapack/zptsv.f, revision 1.1
1.1 ! bertrand 1: SUBROUTINE ZPTSV( N, NRHS, D, E, B, LDB, INFO )
! 2: *
! 3: * -- LAPACK routine (version 3.2) --
! 4: * -- LAPACK is a software package provided by Univ. of Tennessee, --
! 5: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
! 6: * November 2006
! 7: *
! 8: * .. Scalar Arguments ..
! 9: INTEGER INFO, LDB, N, NRHS
! 10: * ..
! 11: * .. Array Arguments ..
! 12: DOUBLE PRECISION D( * )
! 13: COMPLEX*16 B( LDB, * ), E( * )
! 14: * ..
! 15: *
! 16: * Purpose
! 17: * =======
! 18: *
! 19: * ZPTSV computes the solution to a complex system of linear equations
! 20: * A*X = B, where A is an N-by-N Hermitian positive definite tridiagonal
! 21: * matrix, and X and B are N-by-NRHS matrices.
! 22: *
! 23: * A is factored as A = L*D*L**H, and the factored form of A is then
! 24: * used to solve the system of equations.
! 25: *
! 26: * Arguments
! 27: * =========
! 28: *
! 29: * N (input) INTEGER
! 30: * The order of the matrix A. N >= 0.
! 31: *
! 32: * NRHS (input) INTEGER
! 33: * The number of right hand sides, i.e., the number of columns
! 34: * of the matrix B. NRHS >= 0.
! 35: *
! 36: * D (input/output) DOUBLE PRECISION array, dimension (N)
! 37: * On entry, the n diagonal elements of the tridiagonal matrix
! 38: * A. On exit, the n diagonal elements of the diagonal matrix
! 39: * D from the factorization A = L*D*L**H.
! 40: *
! 41: * E (input/output) COMPLEX*16 array, dimension (N-1)
! 42: * On entry, the (n-1) subdiagonal elements of the tridiagonal
! 43: * matrix A. On exit, the (n-1) subdiagonal elements of the
! 44: * unit bidiagonal factor L from the L*D*L**H factorization of
! 45: * A. E can also be regarded as the superdiagonal of the unit
! 46: * bidiagonal factor U from the U**H*D*U factorization of A.
! 47: *
! 48: * B (input/output) COMPLEX*16 array, dimension (LDB,N)
! 49: * On entry, the N-by-NRHS right hand side matrix B.
! 50: * On exit, if INFO = 0, the N-by-NRHS solution matrix X.
! 51: *
! 52: * LDB (input) INTEGER
! 53: * The leading dimension of the array B. LDB >= max(1,N).
! 54: *
! 55: * INFO (output) INTEGER
! 56: * = 0: successful exit
! 57: * < 0: if INFO = -i, the i-th argument had an illegal value
! 58: * > 0: if INFO = i, the leading minor of order i is not
! 59: * positive definite, and the solution has not been
! 60: * computed. The factorization has not been completed
! 61: * unless i = N.
! 62: *
! 63: * =====================================================================
! 64: *
! 65: * .. External Subroutines ..
! 66: EXTERNAL XERBLA, ZPTTRF, ZPTTRS
! 67: * ..
! 68: * .. Intrinsic Functions ..
! 69: INTRINSIC MAX
! 70: * ..
! 71: * .. Executable Statements ..
! 72: *
! 73: * Test the input parameters.
! 74: *
! 75: INFO = 0
! 76: IF( N.LT.0 ) THEN
! 77: INFO = -1
! 78: ELSE IF( NRHS.LT.0 ) THEN
! 79: INFO = -2
! 80: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
! 81: INFO = -6
! 82: END IF
! 83: IF( INFO.NE.0 ) THEN
! 84: CALL XERBLA( 'ZPTSV ', -INFO )
! 85: RETURN
! 86: END IF
! 87: *
! 88: * Compute the L*D*L' (or U'*D*U) factorization of A.
! 89: *
! 90: CALL ZPTTRF( N, D, E, INFO )
! 91: IF( INFO.EQ.0 ) THEN
! 92: *
! 93: * Solve the system A*X = B, overwriting B with X.
! 94: *
! 95: CALL ZPTTRS( 'Lower', N, NRHS, D, E, B, LDB, INFO )
! 96: END IF
! 97: RETURN
! 98: *
! 99: * End of ZPTSV
! 100: *
! 101: END
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