1 Introduction

This is the detailed user's guide for the C binding of the QDP Data Parallel Applications Programmer Interface developed under the auspices of the U.S. Department of Energy Scientific Discovery through Advanced Computing (SciDAC) program.

The QDP Level 2 API has the following features:

• Can specify a physical lattice of any size and number of dimensions.
• Automatically handles the layout of the lattice across the machine.
• Provides functions for creating and destroying fields on the lattice along with a large set of data parallel operations (logically SIMD) acting on all sites across the lattice or on subsets of these sites.
• Allows creation of arbitrary subsets of sites.
• All math operations are handled by the SciDAC QLA library which has optimized versions for SSE (Intel, AMD) and 440 (QCDOC, BG/L) architectures.
• Allows asynchronous (non-blocking) shifts of lattice level objects over any permutation map of sites onto sites.
• Automatically handles dependency of shifts and waits on the results only when needed.
• Uses the SciDAC QMP library for communications which is available for all MPI platforms and QCDOC.
• Provides some combined shift and linear algebra instructions for convenience and optimization.
• Provides fill operations (filling a lattice quantity from a scalar value(s)), global reduction operations, and lattice-wide operations on various data-type primitives, such as matrices, vectors and propagators.
• Has flexible I/O capabilities allowing reading and writing of all lattice fields and also global data.
• Uses SciDAC QIO library for I/O which is compatible with the USQCD and ILDG standards.