"The objectives of STXXL project (distinguishing it from other libraries):
• Make the library able to handle problems of real world size (up to dozens of
terabytes).
• Offer transparent support of parallel disks. This feature although announced
has not been implemented in any library.
• Implement parallel disk algorithms. LEDA-SM and TPIE libraries offer only
implementations of single disk EM algorithms.
• Use computer resources more efficiently. STXXL allows transparent overlapping
of I/O and computation in many algorithms and data structures.
• Care about constant factors in I/O volume. A unique library feature “pipelining”
can half the number of I/Os performed by an algorithm.
• Care about the internal work, improve the in-memory algorithms. Having many
disks can hide the latency and increase the I/O bandwidth, s.t. internal work
becomes a bottleneck.
• Care about operating system overheads. Use unbuffered disk access to avoid
superfluous copying of data.
• Shorten development times providing well known interface for EM algorithms
and data structures. We provide STL-compatible2 interfaces for our implementations."
Not just about the usefulness of this library but the theoretical and practical aspects of the research. This tutorial clarifies the goals in the first pages: http://algo2.iti.kit.edu/dementiev/files/stxxl_tutorial.pdf