This class performs DEFLATE compression through writing. For more information on the Deflate algorithm, see IETF RFC 1951, "DEFLATE Compressed Data Format Specification version 1.3."
This class is similar to Ionic.Zlib.DeflateStream, except that this class is for compression only, and this implementation uses an approach that employs multiple worker threads to perform the DEFLATE. On a multi-cpu or multi-core computer, the performance of this class can be significantly higher than the single-threaded DeflateStream, particularly for larger streams. How large? Anything over 10mb is a good candidate for parallel compression.
The tradeoff is that this class uses more memory and more CPU than the vanilla DeflateStream, and also is less efficient as a compressor. For large files the size of the compressed data stream can be less than 1% larger than the size of a compressed data stream from the vanialla DeflateStream. For smaller files the difference can be larger. The difference will also be larger if you set the BufferSize to be lower than the default value. Your mileage may vary. Finally, for small files, the ParallelDeflateOutputStream can be much slower than the vanilla DeflateStream, because of the overhead associated to using the thread pool.