The block-tridiagonal matrix $a$ (with $M$ by $M$ blocks) of linear
system $a y = b$ is assumed partitioned into five (coupled) subsets
of the respective partitioning sizes $1$, $p$, $q-p+1$, $N-q-1$ and
$1$. The three internal subsets themselves are then assumed
tractable by the three different algorithms taken from Refs. {1],
{2] and [3], respectively. In a direct continuation of Refs. [4] and
[5] the so called hybrid algorithm (imposing the coupling among
sub-solutions and matching the partitions) is then proposed and
tested.

MR2604610 Stel'makh, S. N. On the composition of numerical methods
for solving three-point difference equations. (Russian) Vestsi Nats.
Akad. Navuk Belarusi Ser. Fiz.-Mat. Navuk 2009, no. 2, 17--23, 125.
65Q10