  With the proliferation of domain-specific models, model merging has emerged
as a set of techniques that combine the capabilities of multiple models into
one that can multitask without the cost of additional training. In this paper,
we propose a new model merging technique, Drop and rEscaLe via sampLing with
mAgnitude (DELLA-Merging), that employs a novel pruning technique, MAGPRUNE,
which shows significant advantages over DARE and TIES. MAGPRUNE first ranks the
parameters in order of their magnitude and assigns higher dropout probabilities
(p) to parameters with lower ranks corresponding to lower magnitudes. To
approximate the original embeddings, MAGPRUNE employs a rescaling operation on
the parameters that survive the random dropping by 1/(1 - p). On three
different expert models considered for merging (LM, Math, Code) and
corresponding benchmark datasets (AlpacaEval, GSM8K, MBPP), DELLA shows an
average improvement of 2.4 points over baseline methods employing delta
parameter pruning (an improvement of 3.6 points over TIES, 1.2 points over
DARE), and 11.1 points over the no-pruning baseline (TA). We release the source
code at: https://github.com/declare-lab/della.
