Although the optimized lazy implementation improves significantly the efficiency of the resulting program over the pure lazy approach, it was found that little parallelism can effectively be identified. This remains true even when a new notion of laziness --- speculative laziness --- is introduced, notion well suited to parallel machines as it based on a parallel notion of head-strictness instead of the traditional sequential one.
Our experiments also showed that when a program's result is known to be finite, then strictness analysis can generate almost as much parallelism as can be obtained from a lenient (i.e., non-strict but non-lazy) implementation. Thus, this means strictness analysis per se is not sufficient and should be combined with some form of termination analysis and that there is little hope to extract much parallelism for programs that really require laziness.