dlassq (l) - Linux Manuals

dlassq: returns the values scl and smsq such that ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,

NAME

DLASSQ - returns the values scl and smsq such that ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,

SYNOPSIS

SUBROUTINE DLASSQ(
N, X, INCX, SCALE, SUMSQ )

    
INTEGER INCX, N

    
DOUBLE PRECISION SCALE, SUMSQ

    
DOUBLE PRECISION X( * )

PURPOSE

DLASSQ returns the values scl and smsq such that where x( i ) = X( 1 + ( i - 1 )*INCX ). The value of sumsq is assumed to be non-negative and scl returns the value

scl = max( scale, abs( x( i ) ) ).
scale and sumsq must be supplied in SCALE and SUMSQ and
scl and smsq are overwritten on SCALE and SUMSQ respectively. The routine makes only one pass through the vector x.

ARGUMENTS

N (input) INTEGER
The number of elements to be used from the vector X.
X (input) DOUBLE PRECISION array, dimension (N)
The vector for which a scaled sum of squares is computed. x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
INCX (input) INTEGER
The increment between successive values of the vector X. INCX > 0.
SCALE (input/output) DOUBLE PRECISION
On entry, the value scale in the equation above. On exit, SCALE is overwritten with scl , the scaling factor for the sum of squares.
SUMSQ (input/output) DOUBLE PRECISION
On entry, the value sumsq in the equation above. On exit, SUMSQ is overwritten with smsq , the basic sum of squares from which scl has been factored out.

Pages related to dlassq

  • dlassq (3)
  • dlas2 (l) - computes the singular values of the 2-by-2 matrix [ F G ] [ 0 H ]
  • dlascl (l) - multiplies the M by N real matrix A by the real scalar CTO/CFROM
  • dlascl2 (l) - performs a diagonal scaling on a vector
  • dlasd0 (l) - a divide and conquer approach, DLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal N-by-M matrix B with diagonal D and offdiagonal E, where M = N + SQRE
  • dlasd1 (l) - computes the SVD of an upper bidiagonal N-by-M matrix B,
  • dlasd2 (l) - merges the two sets of singular values together into a single sorted set
  • dlasd3 (l) - finds all the square roots of the roots of the secular equation, as defined by the values in D and Z
  • dlasd4 (l) - subroutine compute the square root of the I-th updated eigenvalue of a positive symmetric rank-one modification to a positive diagonal matrix whose entries are given as the squares of the corresponding entries in the array d, and that 0 <= D(i) < D(j) for i < j and that RHO > 0
  • dlasd5 (l) - subroutine compute the square root of the I-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 diagonal matrix diag( D ) * diag( D ) + RHO The diagonal entries in the array D are assumed to satisfy 0 <= D(i) < D(j) for i < j