Vector Math Library Functions                        vlog(3MVEC)



NAME
     vlog, vlogf - vector logarithm functions

SYNOPSIS
     cc [ flag... ] file... -lmvec [ library... ]

     void vlog(int *n, double * restrict x, int *stridex,
          double * restrict y, int *stridey);


     void vlogf(int *n, float * restrict x, int *stridex,
          float * restrict y, int *stridey);


DESCRIPTION
     These functions evaluate the function log(x) for  an  entire
     vector  of values at once. The first parameter specifies the
     number of values to compute. Subsequent  parameters  specify
     the argument and result vectors. Each vector is described by
     a pointer to the first element and a stride,  which  is  the
     increment between successive elements.


     Specifically, vlog(n, x, sx, y, sy) computes y[i *  *sy]  =
     log(x[i * *sx]) for each i = 0, 1, ..., *n - 1. The vlogf()
     function performs the same computation for single  precision
     data.


     These functions are not guaranteed to deliver  results  that
     are  identical to the results of the log(3M) functions given
     the same arguments. Non-exceptional  results,  however,  are
     accurate to within a unit in the last place.

USAGE
     The element count *n must be greater than zero. The  strides
     for   the  argument  and  result  arrays  can  be  arbitrary
     integers, but the arrays themselves must not be the same  or
     overlap.  A zero stride effectively collapses an entire vec-
     tor into a single element. A negative stride causes a vector
     to be accessed in descending memory order, but note that the
     corresponding pointer must still point to the first  element
     of  the  vector  to be used; if the stride is negative, this
     will be the highest-addressed element in memory.  This  con-
     vention differs from the Level 1 BLAS, in which array param-
     eters always refer to the lowest-addressed element in memory
     even when negative increments are used.


     These functions assume  that  the  default  round-to-nearest
     rounding  direction  mode  is in effect. On x86, these func-
     tions also assume that the default round-to-64-bit  rounding



SunOS 5.11          Last change: 14 Dec 2007                    1






Vector Math Library Functions                        vlog(3MVEC)



     precision  mode is in effect. The result of calling a vector
     function with a non-default rounding mode in effect is unde-
     fined.


     These functions handle special cases and exceptions  in  the
     same  way as the log() functions when c99 MATHEREXCEPT con-
     ventions are in effect. See log(3M) for the results for spe-
     cial cases.


     An application wanting to check for exceptions  should  call
     feclearexcept(FEALEXCEPT) before calling these functions.
     On  return,  if  fetestexcept(FEINVALID    FEDIVBYZERO  
     FEOVERFLOW    FEUNDERFLOW)  is non-zero, an exception has
     been raised. The application can then examine the result  or
     argument  vectors  for exceptional values. Some vector func-
     tions can raise the inexact exception even if  all  elements
     of  the  argument  array are such that the numerical results
     are exact.

ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Committed                   
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     log(3M), feclearexcept(3M), fetestexcept(3M), attributes(5)

















SunOS 5.11          Last change: 14 Dec 2007                    2