LAPACK  3.8.0 LAPACK: Linear Algebra PACKage

## ◆ zpotri()

 subroutine zpotri ( character UPLO, integer N, complex*16, dimension( lda, * ) A, integer LDA, integer INFO )

ZPOTRI

Purpose:
``` ZPOTRI computes the inverse of a complex Hermitian positive definite
matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
computed by ZPOTRF.```
Parameters
 [in] UPLO ``` UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored.``` [in] N ``` N is INTEGER The order of the matrix A. N >= 0.``` [in,out] A ``` A is COMPLEX*16 array, dimension (LDA,N) On entry, the triangular factor U or L from the Cholesky factorization A = U**H*U or A = L*L**H, as computed by ZPOTRF. On exit, the upper or lower triangle of the (Hermitian) inverse of A, overwriting the input factor U or L.``` [in] LDA ``` LDA is INTEGER The leading dimension of the array A. LDA >= 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 (i,i) element of the factor U or L is zero, and the inverse could not be computed.```
Date
December 2016

Definition at line 97 of file zpotri.f.

97 *
98 * -- LAPACK computational routine (version 3.7.0) --
99 * -- LAPACK is a software package provided by Univ. of Tennessee, --
100 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
101 * December 2016
102 *
103 * .. Scalar Arguments ..
104  CHARACTER uplo
105  INTEGER info, lda, n
106 * ..
107 * .. Array Arguments ..
108  COMPLEX*16 a( lda, * )
109 * ..
110 *
111 * =====================================================================
112 *
113 * .. External Functions ..
114  LOGICAL lsame
115  EXTERNAL lsame
116 * ..
117 * .. External Subroutines ..
118  EXTERNAL xerbla, zlauum, ztrtri
119 * ..
120 * .. Intrinsic Functions ..
121  INTRINSIC max
122 * ..
123 * .. Executable Statements ..
124 *
125 * Test the input parameters.
126 *
127  info = 0
128  IF( .NOT.lsame( uplo, 'U' ) .AND. .NOT.lsame( uplo, 'L' ) ) THEN
129  info = -1
130  ELSE IF( n.LT.0 ) THEN
131  info = -2
132  ELSE IF( lda.LT.max( 1, n ) ) THEN
133  info = -4
134  END IF
135  IF( info.NE.0 ) THEN
136  CALL xerbla( 'ZPOTRI', -info )
137  RETURN
138  END IF
139 *
140 * Quick return if possible
141 *
142  IF( n.EQ.0 )
143  \$ RETURN
144 *
145 * Invert the triangular Cholesky factor U or L.
146 *
147  CALL ztrtri( uplo, 'Non-unit', n, a, lda, info )
148  IF( info.GT.0 )
149  \$ RETURN
150 *
151 * Form inv(U) * inv(U)**H or inv(L)**H * inv(L).
152 *
153  CALL zlauum( uplo, n, a, lda, info )
154 *
155  RETURN
156 *
157 * End of ZPOTRI
158 *
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:55
subroutine zlauum(UPLO, N, A, LDA, INFO)
ZLAUUM computes the product UUH or LHL, where U and L are upper or lower triangular matrices (blocked...
Definition: zlauum.f:104
subroutine ztrtri(UPLO, DIAG, N, A, LDA, INFO)
ZTRTRI
Definition: ztrtri.f:111
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
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