We describe the new software package GELDA for the numerical
solution of linear differential-algebraic equations with variable
coefficients. The implementation is based on the new discretization
scheme introduced in an earlier paper of the first two authors. 
It can deal with systems of
arbitrary index and with systems that do not have unique solutions
or inconsistencies in the initial values or the inhomogeneity.

The package includes a computation of all the local invariants of
the system, a regularization procedure and an index reduction scheme
and it can be combined with every solution method for standard index 1 
systems. Nonuniqueness and inconsistencies are treated in a least
square sense.

We give a brief survey of the theoretical analysis of linear
differential-algebraic equations with variable coefficients and
discuss the algorithms used in GELDA. Furthermore, we include a
series of numerical examples as well as comparisons with results
from other codes, as far as this is possible.
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