scipy.linalg.lapack.dlasd4

scipy.linalg.lapack.dlasd4(i, d, z, rho=1.0) = <flapack function dlasd4>

Compute one root of the secular equation of a rank-one modified diagonal matrix (LAPACK dlasd4).

Used by the divide-and-conquer SVD update. LAPACK ships no complex counterpart, so only the real flavors exist.

Parameters:

iint

Which root to compute, 0-based.

dndarray

The diagonal, in increasing order.

zndarray

The rank-one update vector, the same length as d.

rhofloat, optional

Scalar the update is scaled by. Default is 1.0.

Returns:

deltandarray

The differences d[j] - sigma.

sigmafloat

The computed root.

workndarray

The sums d[j] + sigma.

infoint

0 on success; 1 if the iteration failed to converge.