Accelerate.framework provides vector log and exp functionality. See
vfp.h.
I just noticed that vecLib/vfp.h is a cornucopia of mathematical
functions, not just exp and log. For example, the first three are
vdivf C = A ÷ B
vsqrtf B = √A
vrsqrtf B = 1/√A
In an earlier thread "Fast atan2" I sought, with partial success, a
version of atan2 to meet certain speed and accuracy reqirements.
Nobody mentioned vfp.h, but a look at that header file reveals a full
suite of trig and inverse functions, including
vatan2f Computes the arc tangent of y/x in [-pi,pi] using
the sign of both arguments to determine the
quadrant of the computed value.
A good first step when looking for AltiVec math functions would be to
read vecLib/vfp.h. All functions are
AVAILABLE_MAC_OS_X_VERSION_10_0_AND_LATER. You can even call them
from a CFM application merely by linking to vecLib.
New for Tiger is a faster one that operates on long arrays, part of
vForce.
vForce could use some better advertising, too :-)
In OS X 10.4 vecLib/vForce.h is a well-chosen set of math array
functions, each being supplied in float and double forms. AltiVec is
used internally by the float forms. The functions are array versions
of the "the top 20 singles" from fp.h, with a few handy extras. A
sample:
/* Set z[i] to y[i]/x[i], for i=0,..,n-1 */
void vvdivf (...);
void vvdiv (...);
/* Set y[i] to the exponential function of x[i], for i=0,..,n-1 */
void vvexpf (...);
void vvexp (...);
/* Set z[i] to the arctangent of y[i]/x[i], for i=0,..,n-1 */
void vvatan2f (...);
void vvatan2 (...);
Neither vatan2f nor vvatan2f can be found in Documentation API
searches in Xcode 2, hence the need for more publicity...
Robert P.
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