1. A computer-implemented method, comprising: preparing a portable code sequence corresponding to a source representation of code comprising an atomic transaction; and generating a functional sequence executable to perform the atomic transaction in a target execution environment; wherein said preparing comprises: including in the portable code sequence an operation defined by a portable transaction interface; and wherein said generating a functional sequence comprises: including in the functional sequence a call to a function executable to implement the operation defined by the portable transaction interface in the target execution environment dependent on availability of best effort transactional memory support mechanisms in the target execution environment.