diff options
| author | igor175 <igor175@8a072113-8704-0410-8d35-dd094bca7971> | 2012-12-12 02:08:16 +0000 |
|---|---|---|
| committer | igor175 <igor175@8a072113-8704-0410-8d35-dd094bca7971> | 2012-12-12 02:08:16 +0000 |
| commit | d9f63ada777008e843da65f6d74b9237141f4f1d (patch) | |
| tree | e6e40825878d84f13cf74a55842d1eff99bfef31 /SRC/zsytf2.f | |
| parent | 315b545f709de1ea5e9079d9f8b97caab0cc46a2 (diff) | |
Updated comments in (s,d,c,z)sytf2.f and (c,z)hetf2.f
Diffstat (limited to 'SRC/zsytf2.f')
| -rw-r--r-- | SRC/zsytf2.f | 35 |
1 files changed, 24 insertions, 11 deletions
diff --git a/SRC/zsytf2.f b/SRC/zsytf2.f index cf604ecf..23564091 100644 --- a/SRC/zsytf2.f +++ b/SRC/zsytf2.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 @@ -273,7 +282,8 @@ ABSAKK = CABS1( 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 = IZAMAX( K-1, A( 1, K ), 1 ) @@ -284,7 +294,8 @@ * IF( MAX( ABSAKK, COLMAX ).EQ.ZERO .OR. DISNAN(ABSAKK) ) THEN * -* Column K is zero or 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 @@ -441,7 +452,8 @@ ABSAKK = CABS1( 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 + IZAMAX( N-K, A( K+1, K ), 1 ) @@ -452,7 +464,8 @@ * IF( MAX( ABSAKK, COLMAX ).EQ.ZERO .OR. DISNAN(ABSAKK) ) THEN * -* Column K is zero or 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 |