Accelerate man page on MacOSX

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ACCELERATE(7)	     BSD Miscellaneous Information Manual	 ACCELERATE(7)

NAME
     Accelerate vecLib vImage Neon vMathLib BLAS LAPACK vDSP Vector
     Computation Extended Math Library — This man page introduces the Acceler‐
     ate umbrella framework, its constituent libraries and programming support
     in Mac OS X.

DESCRIPTION
     The Accelerate framework (/System/Library/Frameworks/Accelerate.frame‐
     work) contains thousands of hand tuned high performance library routines
     for common problems in signal and image processing and general and scien‐
     tific computing.  These routines are provided to help developers and
     Apple frameworks alike make better use of onboard hardware SIMD vector
     engines (such as SSE and Neon) and multiple processors for best perfor‐
     mance, without the need to invest in the complexity that SIMD and multi‐
     threaded programming sometimes requires.

     A typical Accelerate.framework function will be presented as a single
     function that accomplishes a task -- e.g. do a discrete Fourier trans‐
     form, or blur an image, or perhaps just multiply two arrays of floats
     together. Once called, a typical Accelerate.framework function will exam‐
     ine available hardware and select a tuned version of the algorithm for
     best performance on that hardware for that problem size, image shape,
     etc.  That function will usually be hand-tuned vectorized code (i.e. uses
     SSE or Neon). For large enough problems, the function may automatically
     split up the work across multiple processors using Grand Central Dispatch
     (GCD) or pthreads, all without involvement of the caller. The speedups so
     obtained can be quite significant due to impressive synergies between
     SIMD vector engines and multithreading.  Vectorization typically will
     enchance performance many fold -- 2, 4, or even 10 fold improvement is
     normal. Multithreading can then further accelerate your code many fold
     according to the number of processors on your system. Some vectorized,
     multithreaded Accelerate.framework functions run hundreds of times faster
     than their scalar, single threaded counterparts!

     Accelerate.framework is intended to help you towards greater application
     performance regardless of your current investment in high performance
     technologies.  If you have already written your own threading engine, you
     can use methods such as the kvImageDoNotTile flag or the VECLIB_MAXI‐
     MUM_THREADS environment variable to disable internal multithreading so
     that it does not contend with your threading engine. If you have pseudo-
     real-time scheduling needs, Accelerate.framework functions that otherwise
     might allocate their own temporary memory on the heap allow you to pass
     in preallocated temporary buffers, so as to avoid potential locking in
     malloc. If you are interested in writing your own vector code, perhaps to
     speed up areas of your application which is not covered by Accelerate
     functionality, the framework headers provide cross platform vector types
     that you can use to enhance the portability of some vector code and
     facilitate debugging, as well as a number of basic library routines to
     make writing vector code easier, such as the interfaces found in vMath‐
     Lib, a library of math routines (e.g. sin, cos, pow, etc.) for SIMD vec‐
     tors.

     To use Accelerate.framework headers:
	  #include <Accelerate/Accelerate.h>

     To link to Accelerate.framework, simply add -framework Accelerate to your
     compiler line:
	  cc -framework Accelerate my_file.c

     For help with linking to frameworks in Xcode, see also:
	  http://developer.apple.com/library/mac/#documentation/MacOSX/Concep‐
	  tual/BPFrameworks/Tasks/IncludingFrameworks.html

For further information:
     Browse a comprehensive introduction to the Accelerate framework:
	  http://developer.apple.com/performance/accelerateframework.html

Accelerate Umbrella Framework
     The Accelerate umbrella framework encompasses all the libraries provided
     with MacOS X that Apple has optimized for high performance vector and
     numerical computing. Subsequent sections describe the sub-frameworks that
     comprise the Accelerate framework.

     Please link to Accelerate.framework. The positioning of interfaces within
     sub-frameworks and libraries within Accelerate.framework is subject to
     change.

vImage Framework
     This framework is designed to provide a suite of image processing primi‐
     tives. Convolutions, Morphological operators, and Geometric transforms
     (e.g. scale, shear, warp, rotate) are provided. Alpha compositing and
     histogram operations are also supported, in addition to various conver‐
     sion routines between different image formats.  vImage uses your image
     data in place without costly packing and unpacking from wrapper objects,
     using a simple descriptor of the image using base address, height, width
     and row bytes (to allow for tiling and row padding). Four core formats
     are supported:

	  Planar8 - a single channel, 8-bit per channel image
	  ARGB8888 - a four channel, 8-bit per channel image.*
	  PlanarF - a single channel, floating point image.
	  ARGBFFFF - a four channel, floating point image.*

	  *Most functions are channel order agnostic, but where it matters,
	  RGBA and BGRA forms may also be provided.

     Other formats are supported by conversion to core format prior to apply‐
     ing various vImage functions. The conversion cost is typically very
     small, and is in many cases faster than attempting to do the conversion
     just in time within the function, because many redundant conversions  to
     a arithmetic format usable by the core vector units, some hidden from
     you, can be avoided.  The formats provided reflect core performance com‐
     petencies of the vector hardware rather than the wide diversity of image
     formats out there.

     For more information, see:

	   http://developer.apple.com/library/mac/#documentation/Perfor‐
	  mance/Conceptual/vImage/Introduction/Introduction.html

vecLib Framework
     The vecLib framework is a collection of facilities covering digital sig‐
     nal processing (vDSP), matrix computations (BLAS), numerical linear alge‐
     bra (LAPACK) and mathematical routines (vForce/vMathLib)

     The vDSP, BLAS and LAPACK components of vecLib run on the scalar and vec‐
     tor domain.  vecLib automatically detects the presence of the vector
     engine and uses it.  vMathLib mirrors the existing scalar libm on the
     vector engine.  vMathLib runs only on the vector engine.

     For more information, see:

	   http://developer.apple.com/library/mac/#documentation/Perfor‐
	  mance/Conceptual/vecLib/Reference/reference.html

vDSP
     The vDSP Library provides mathematical functions for applications such as
     speech, sound, audio, and video processing, diagnostic medical imaging,
     radar signal processing, seismic analysis, and scientific data process‐
     ing.

     The vDSP functions operate on real and complex data types. The functions
     include data type conversions, fast Fourier transforms (FFTs), and vec‐
     tor-to-vector and vector-to-scalar operations.

     The vDSP functions have been implemented in two ways: as vectorized code,
     using the vector unit on the ARM and Intel microprocessors, and as scalar
     code, which runs on all machines. Vector code often has special alignment
     restrictions. If your data is not properly aligned it is common for vDSP
     to use the scalar path as a fallback. For best results on Intel, align
     your data to a multiple of 16 bytes.  (Malloc naturally aligns memory
     blocks that it allocates to 16 bytes on MacOS X.)

     It is noteworthy that vDSP's FFTs are one of the fastest implementations
     of the Discrete Fourier Transforms available anywhere.

     The vDSP Library itself is included as part of vecLib in Mac OS X.	 The
     header file, vDSP.h, defines data types used by the vDSP functions and
     symbols accepted as flag arguments to vDSP functions.

     vDSP functions are available in single and double precision.  Note that
     only the single precision is vectorized on ARM due to the underlying
     instruction set architecture of the vector engine on board. The Intel
     vector unit supports both single and double precision, so double preci‐
     sion operations can be vectorized on Intel processors.

     For more information about vDSP see:

	  <http://developer.apple.com/hardwaredrivers/ve/down‐
	  loads/vDSP_Library.pdf>

BLAS
     The Basic Linear Algebra Subroutines (BLAS) are high quality, industry
     standard routines for performing basic vector and matrix operations.
     Level 1 BLAS consists of vector-vector operations, Level 2 BLAS consists
     of matrix-vector operations, and Level 3 BLAS have matrix-matrix opera‐
     tions.  The efficiency, portability, and the wide adoption of the BLAS
     have made them commonplace in the development of high quality linear
     algebra software such as LAPACK and in  other technologies requiring fast
     vector and matrix calculations.  All of the industry standard FORTRAN and
     C BLAS entry points, as well as some common extensions, are exported by
     the vecLib framework.

     For more information refer to:

	  <http://www.netlib.org/blas/faq.html>

LAPACK
     LAPACK provides routines for solving systems of simultaneous linear equa‐
     tions, least-squares solutions of linear systems of equations, eigenvalue
     problems, and singular value problems.  The associated matrix factoriza‐
     tions (LU, Cholesky, QR, SVD, Schur, generalized Schur) are also pro‐
     vided, as are related computations such as reordering of the Schur fac‐
     torizations and estimating condition numbers. Dense and banded matrices
     are handled, but not general sparse matrices. In all areas, similar func‐
     tionality is provided for real and complex matrices, in both single and
     double precision.	LAPACK in vecLib makes full use of the optimized BLAS
     and fully benefits from their performance.	 All the industry standard
     FORTRAN LAPACK entry points are exported from the vecLib framework.  C
     programs may make calls to the FORTRAN entry points using the prototypes
     set out in "/System/Library/Frameworks/vecLib.framework/Headers/cla‐
     pack.h".

     For more information, please see:

	  <http://www.netlib.org/lapack/index.html>

     LAPACK follows FORTRAN calling conventions (even when called from C
     code).  Users must be aware that ALL arguments are passed by reference.
     This includes all scalar arguments such as matrix dimensions and scale
     factors.  Additionally, please note that two-dimensional arrays such as
     matrices are stored in column-major order; this differs from how C pro‐
     grammers customarily lay out such arrays.

     For more information refer to <http://www.netlib.org/clapack/readme>.

SEE ALSO
     You may also be interested in the system math library, which provides
     high-quality implementations of basic mathematical functions like exp,
     log, pow, sin, cos...  See math(3) for more information.

BUGS
     Accelerate.framework is not magic! It will not vectorize or multithread
     your code for you, just because you linked against the framework.	You
     have to actually call the functions exported by the Accelerate.framework,
     and then only those functions from the framework that you called will be
     Accelerated.

MacOS X				  May 1, 2007			       MacOS X
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