||Fortran, long the epitome of stability, is once again a language in flux. Fortran 90 is not just the long-awaited updating of traditional Fortran 77 to modern computing practices, but also demonstrates Fortran's decisive bid to be the language of choice for parallel programming on multiprocessor computers.
At the same time, Fortran 90 is completely backwards-compatible with all Fortran 77 code. So, users with legacy code, or who choose to use only older language constructs, will still get the benefit of updated and actively maintained compilers.
As we, the authors of Numerical Recipes, watched the gestation and birth of Fortran 90 by its governing standards committee (an interesting process described by a leading Committee member, Michael Metcalf, in the Foreword to our Volume 2), it became clear to us that the right moment for moving Numerical Recipes from Fortran 77 to Fortran 90 was sooner, rather than later.
On the other hand, it was equally clear that Fortran-77-style programming — no matter whether with Fortran 77 or Fortran 90 compilers — is, and will continue for a long time to be, the "mother tongue" of a large population of active scientists, engineers, and other users of numerical computation. This is not a user base that we would willingly or knowingly abandon.
The solution was immediately clear: a two-volume edition of the Fortran Numerical Recipes consisting of Volume 1 (this one, a corrected reprinting of the previous one-volume edition), now retitled Numerical Recipes in Fortran 77, and a completely new Volume 2, titled Numerical Recipes in Fortran 90: The Art of Parallel Scientific Computing. Volume 2 begins with three chapters (21, 22, and 23) that extend the narrative of the first volume to the new subjects of Fortran 90 language features, parallel programming methodology, and the implementation of certain useful utility functions in Fortran 90. Then, in exact correspondence with Volume l's Chapters 1-20, are new chapters B1-B20, devoted principally to the listing and explanation of new Fortran 90 routines. With a few exceptions, each Fortran 77 routine in Volume 1 has a corresponding new Fortran 90 version in Volume 2. (The exceptions are a few new capabilities, notably in random number generation and in multigrid PDE solvers, that are unique to Volume 2's Fortran 90.) Otherwise, there is no duplication between the volumes. The detailed explanation of the algorithms in this Volume 1 is intended to apply to, and be essential for, both volumes.
In other words: You can use this Volume 1 without having Volume 2, but you can't use Volume 2 without Volume 1. We think that there is much to be gained by having and using both volumes: Fortran 90's parallel language constructions are not only useful for present and future multiprocessor machines; they also allow for the elegant and concise formulation of many algorithms on ordinary single-processor computers. We think that essentially all Fortran programmers will want gradually to migrate into Fortran 90 and into a mode of "thinking parallel." We have written Volume 2 specifically to help with this important transition.
Volume 2's discussion of parallel programming is focused on those issues of direct relevance to the Fortran 90 programmer. Some more general aspects of parallel programming, such as communication costs, synchronization of multiple processers, etc., are touched on only briefly. We provide references to the extensive literature on these more specialized topics.