What are the benefits of usage of frameworks such as MPI?

a$.$ they create virtualization layer allowing constructing different logical distributed,

architectures of computing nodes on any given physical network of computers

b$.$ they offer a set of communication functions usable for parallel programming,

c$.$ they include set of functions solving typical computational problems in distributed manner,

like distributed matrix multiplication, distributed sorting with Fox algorithm, etc.,

d$.$ they offer a set of synchronization mechanisms usable for parallel programming.