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author | igor175 <igor175@8a072113-8704-0410-8d35-dd094bca7971> | 2012-12-12 02:08:16 +0000 |
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committer | igor175 <igor175@8a072113-8704-0410-8d35-dd094bca7971> | 2012-12-12 02:08:16 +0000 |
commit | d9f63ada777008e843da65f6d74b9237141f4f1d (patch) | |
tree | e6e40825878d84f13cf74a55842d1eff99bfef31 /SRC/dsytf2.f | |
parent | 315b545f709de1ea5e9079d9f8b97caab0cc46a2 (diff) | |
download | lapack-d9f63ada777008e843da65f6d74b9237141f4f1d.tar.gz lapack-d9f63ada777008e843da65f6d74b9237141f4f1d.tar.bz2 lapack-d9f63ada777008e843da65f6d74b9237141f4f1d.zip |
Updated comments in (s,d,c,z)sytf2.f and (c,z)hetf2.f
Diffstat (limited to 'SRC/dsytf2.f')
-rw-r--r-- | SRC/dsytf2.f | 35 |
1 files changed, 24 insertions, 11 deletions
diff --git a/SRC/dsytf2.f b/SRC/dsytf2.f index 23d8889d..3a90da85 100644 --- a/SRC/dsytf2.f +++ b/SRC/dsytf2.f @@ -90,13 +90,22 @@ *> \verbatim *> IPIV is INTEGER array, dimension (N) *> Details of the interchanges and the block structure of D. -*> If IPIV(k) > 0, then rows and columns k and IPIV(k) were -*> interchanged and D(k,k) is a 1-by-1 diagonal block. -*> If UPLO = 'U' and IPIV(k) = IPIV(k-1) < 0, then rows and -*> columns k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) -*> is a 2-by-2 diagonal block. If UPLO = 'L' and IPIV(k) = -*> IPIV(k+1) < 0, then rows and columns k+1 and -IPIV(k) were -*> interchanged and D(k:k+1,k:k+1) is a 2-by-2 diagonal block. +*> +*> If UPLO = 'U': +*> If IPIV(k) > 0, then rows and columns k and IPIV(k) were +*> interchanged and D(k,k) is a 1-by-1 diagonal block. +*> +*> If IPIV(k) = IPIV(k-1) < 0, then rows and columns +*> k-1 and -IPIV(k) were interchanged and D(k-1:k,k-1:k) +*> is a 2-by-2 diagonal block. +*> +*> If UPLO = 'L': +*> If IPIV(k) > 0, then rows and columns k and IPIV(k) were +*> interchanged and D(k,k) is a 1-by-1 diagonal block. +*> +*> If IPIV(k) = IPIV(k+1) < 0, then rows and columns +*> k+1 and -IPIV(k) were interchanged and D(k:k+1,k:k+1) +*> is a 2-by-2 diagonal block. *> \endverbatim *> *> \param[out] INFO @@ -268,7 +277,8 @@ ABSAKK = ABS( A( K, K ) ) * * IMAX is the row-index of the largest off-diagonal element in -* column K, and COLMAX is its absolute value +* column K, and COLMAX is its absolute value. +* Determine both COLMAX and IMAX. * IF( K.GT.1 ) THEN IMAX = IDAMAX( K-1, A( 1, K ), 1 ) @@ -279,7 +289,8 @@ * IF( (MAX( ABSAKK, COLMAX ).EQ.ZERO) .OR. DISNAN(ABSAKK) ) THEN * -* Column K is zero or contains a NaN: set INFO and continue +* Column K is zero or underflow, or contains a NaN: +* set INFO and continue * IF( INFO.EQ.0 ) $ INFO = K @@ -436,7 +447,8 @@ ABSAKK = ABS( A( K, K ) ) * * IMAX is the row-index of the largest off-diagonal element in -* column K, and COLMAX is its absolute value +* column K, and COLMAX is its absolute value. +* Determine both COLMAX and IMAX. * IF( K.LT.N ) THEN IMAX = K + IDAMAX( N-K, A( K+1, K ), 1 ) @@ -447,7 +459,8 @@ * IF( (MAX( ABSAKK, COLMAX ).EQ.ZERO) .OR. DISNAN(ABSAKK) ) THEN * -* Column K is zero or contains a NaN: set INFO and continue +* Column K is zero or underflow, or contains a NaN: +* set INFO and continue * IF( INFO.EQ.0 ) $ INFO = K |