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Diffstat (limited to 'SRC/claqsp.f')
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diff --git a/SRC/claqsp.f b/SRC/claqsp.f new file mode 100644 index 00000000..98d0682c --- /dev/null +++ b/SRC/claqsp.f @@ -0,0 +1,141 @@ + SUBROUTINE CLAQSP( UPLO, N, AP, S, SCOND, AMAX, EQUED ) +* +* -- LAPACK auxiliary routine (version 3.1) -- +* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. +* November 2006 +* +* .. Scalar Arguments .. + CHARACTER EQUED, UPLO + INTEGER N + REAL AMAX, SCOND +* .. +* .. Array Arguments .. + REAL S( * ) + COMPLEX AP( * ) +* .. +* +* Purpose +* ======= +* +* CLAQSP equilibrates a symmetric matrix A using the scaling factors +* in the vector S. +* +* Arguments +* ========= +* +* UPLO (input) CHARACTER*1 +* Specifies whether the upper or lower triangular part of the +* symmetric matrix A is stored. +* = 'U': Upper triangular +* = 'L': Lower triangular +* +* N (input) INTEGER +* The order of the matrix A. N >= 0. +* +* AP (input/output) COMPLEX array, dimension (N*(N+1)/2) +* On entry, the upper or lower triangle of the symmetric matrix +* A, packed columnwise in a linear array. The j-th column of A +* is stored in the array AP as follows: +* if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; +* if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. +* +* On exit, the equilibrated matrix: diag(S) * A * diag(S), in +* the same storage format as A. +* +* S (input) REAL array, dimension (N) +* The scale factors for A. +* +* SCOND (input) REAL +* Ratio of the smallest S(i) to the largest S(i). +* +* AMAX (input) REAL +* Absolute value of largest matrix entry. +* +* EQUED (output) CHARACTER*1 +* Specifies whether or not equilibration was done. +* = 'N': No equilibration. +* = 'Y': Equilibration was done, i.e., A has been replaced by +* diag(S) * A * diag(S). +* +* Internal Parameters +* =================== +* +* THRESH is a threshold value used to decide if scaling should be done +* based on the ratio of the scaling factors. If SCOND < THRESH, +* scaling is done. +* +* LARGE and SMALL are threshold values used to decide if scaling should +* be done based on the absolute size of the largest matrix element. +* If AMAX > LARGE or AMAX < SMALL, scaling is done. +* +* ===================================================================== +* +* .. Parameters .. + REAL ONE, THRESH + PARAMETER ( ONE = 1.0E+0, THRESH = 0.1E+0 ) +* .. +* .. Local Scalars .. + INTEGER I, J, JC + REAL CJ, LARGE, SMALL +* .. +* .. External Functions .. + LOGICAL LSAME + REAL SLAMCH + EXTERNAL LSAME, SLAMCH +* .. +* .. Executable Statements .. +* +* Quick return if possible +* + IF( N.LE.0 ) THEN + EQUED = 'N' + RETURN + END IF +* +* Initialize LARGE and SMALL. +* + SMALL = SLAMCH( 'Safe minimum' ) / SLAMCH( 'Precision' ) + LARGE = ONE / SMALL +* + IF( SCOND.GE.THRESH .AND. AMAX.GE.SMALL .AND. AMAX.LE.LARGE ) THEN +* +* No equilibration +* + EQUED = 'N' + ELSE +* +* Replace A by diag(S) * A * diag(S). +* + IF( LSAME( UPLO, 'U' ) ) THEN +* +* Upper triangle of A is stored. +* + JC = 1 + DO 20 J = 1, N + CJ = S( J ) + DO 10 I = 1, J + AP( JC+I-1 ) = CJ*S( I )*AP( JC+I-1 ) + 10 CONTINUE + JC = JC + J + 20 CONTINUE + ELSE +* +* Lower triangle of A is stored. +* + JC = 1 + DO 40 J = 1, N + CJ = S( J ) + DO 30 I = J, N + AP( JC+I-J ) = CJ*S( I )*AP( JC+I-J ) + 30 CONTINUE + JC = JC + N - J + 1 + 40 CONTINUE + END IF + EQUED = 'Y' + END IF +* + RETURN +* +* End of CLAQSP +* + END |