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author | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
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committer | jason <jason@8a072113-8704-0410-8d35-dd094bca7971> | 2008-10-28 01:38:50 +0000 |
commit | baba851215b44ac3b60b9248eb02bcce7eb76247 (patch) | |
tree | 8c0f5c006875532a30d4409f5e94b0f310ff00a7 /SRC/cpptri.f | |
download | lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.gz lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.tar.bz2 lapack-baba851215b44ac3b60b9248eb02bcce7eb76247.zip |
Move LAPACK trunk into position.
Diffstat (limited to 'SRC/cpptri.f')
-rw-r--r-- | SRC/cpptri.f | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/SRC/cpptri.f b/SRC/cpptri.f new file mode 100644 index 00000000..257c3908 --- /dev/null +++ b/SRC/cpptri.f @@ -0,0 +1,130 @@ + SUBROUTINE CPPTRI( UPLO, N, AP, INFO ) +* +* -- LAPACK routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER UPLO + INTEGER INFO, N +* .. +* .. Array Arguments .. + COMPLEX AP( * ) +* .. +* +* Purpose +* ======= +* +* CPPTRI 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 CPPTRF. +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* = 'U': Upper triangular factor is stored in AP; +* = 'L': Lower triangular factor is stored in AP. +* +* N (input) INTEGER +* The order of the matrix A. N >= 0. +* +* AP (input/output) COMPLEX array, dimension (N*(N+1)/2) +* On entry, the triangular factor U or L from the Cholesky +* factorization A = U**H*U or A = L*L**H, packed columnwise as +* a linear array. The j-th column of U or L is stored in the +* array AP as follows: +* if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; +* if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n. +* +* On exit, the upper or lower triangle of the (Hermitian) +* inverse of A, overwriting the input factor U or L. +* +* INFO (output) 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. +* +* ===================================================================== +* +* .. Parameters .. + REAL ONE + PARAMETER ( ONE = 1.0E+0 ) +* .. +* .. Local Scalars .. + LOGICAL UPPER + INTEGER J, JC, JJ, JJN + REAL AJJ +* .. +* .. External Functions .. + LOGICAL LSAME + COMPLEX CDOTC + EXTERNAL LSAME, CDOTC +* .. +* .. External Subroutines .. + EXTERNAL CHPR, CSSCAL, CTPMV, CTPTRI, XERBLA +* .. +* .. Intrinsic Functions .. + INTRINSIC REAL +* .. +* .. Executable Statements .. +* +* Test the input parameters. +* + INFO = 0 + UPPER = LSAME( UPLO, 'U' ) + IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN + INFO = -1 + ELSE IF( N.LT.0 ) THEN + INFO = -2 + END IF + IF( INFO.NE.0 ) THEN + CALL XERBLA( 'CPPTRI', -INFO ) + RETURN + END IF +* +* Quick return if possible +* + IF( N.EQ.0 ) + $ RETURN +* +* Invert the triangular Cholesky factor U or L. +* + CALL CTPTRI( UPLO, 'Non-unit', N, AP, INFO ) + IF( INFO.GT.0 ) + $ RETURN + IF( UPPER ) THEN +* +* Compute the product inv(U) * inv(U)'. +* + JJ = 0 + DO 10 J = 1, N + JC = JJ + 1 + JJ = JJ + J + IF( J.GT.1 ) + $ CALL CHPR( 'Upper', J-1, ONE, AP( JC ), 1, AP ) + AJJ = AP( JJ ) + CALL CSSCAL( J, AJJ, AP( JC ), 1 ) + 10 CONTINUE +* + ELSE +* +* Compute the product inv(L)' * inv(L). +* + JJ = 1 + DO 20 J = 1, N + JJN = JJ + N - J + 1 + AP( JJ ) = REAL( CDOTC( N-J+1, AP( JJ ), 1, AP( JJ ), 1 ) ) + IF( J.LT.N ) + $ CALL CTPMV( 'Lower', 'Conjugate transpose', 'Non-unit', + $ N-J, AP( JJN ), AP( JJ+1 ), 1 ) + JJ = JJN + 20 CONTINUE + END IF +* + RETURN +* +* End of CPPTRI +* + END |