This paper presents a new library for the ProActive environment, called AIL-PA (Asynchronous Iterative Library for ProActive). This new library allows to execute programs for solving large scale problems on various architectures. Two models of algorithm can be used: the synchronous iteration model which is efficient on single clusters; the asynchronous iteration model which is more efficient on distributed clusters. Both approaches are tested on both architectures, using Kernel CG of the NAS Parallel Benchmarks on the Grid'5000 platform. These tests also allow them to compare ProActive with AIL-PA and with the Jace programming environment.