XL Fortran Enterprise Edition for AIX : User's Guide - IBM

Table 34. MASS Vector Library Functions (continued)
vtanh vstanh (y,x,n) Sets y(i) to the hyperbolic
tangent of x(i), for i=1,..,n
The following example shows interface declarations for some of the MASS
double-precision vector functions:
interface
subroutine vsqrt (y, x, n)
real*8 y(*), x(*)
integer n ! Sets y(i) to the square root of x(i), for i=1,..,n
end subroutine vsqrt
subroutine vrsqrt (y, x, n)
real*8 y(*), x(*)
integer n ! Sets y(i) to the reciprocal of the square root of x(i),
! for i=1,..,n
end subroutine vrsqrt
end interface
The following example shows interface declarations for some of the MASS
single-precision vector functions:
interface
subroutine vssqrt (y, x, n)
real*4 y(*), x(*)
integer n ! Sets y(i) to the square root of x(i), for i=1,..,n
end subroutine vssqrt
subroutine vsrsqrt (y, x, n)
real*4 y(*), x(*)
integer n ! Sets y(i) to the reciprocal of the square root of x(i),
! for i=1,..,n
end subroutine vsrsqrt
end interface
The functions vatan2, vdiv, and vpow take four parameters and are of the form
function_name(z,x,y,n). The function vsincos takes four parameters of the form
function_name(y,z,x,n). The function vatan2 outputs a vector z whose elements are
atan(x(i)/y(i)). The function vdiv outputs a vector z whose elements are x(i)/y(i),
with i=1,..,n. The function vsincos outputs two vectors, y and z, whose elements
are sin(x(i)) and cos(x(i)) respectively.
In vcosisin(y,x,n), x is a vector of n real*8 elements and the function outputs a
vector y of n complex*16 elements of the form (cos(x(i)),sin(x(i))).
Consistency of MASS Vector Functions
In the interest of speed, the MASS libraries make certain trade-offs. One of these
involves the consistency of certain MASS vector functions. For certain functions, it
is possible that the result computed for a particular input value will vary slightly
(usually only in the least significant bit) depending on its position in the vector, the
vector length, and nearby elements of the input vector. Also, the results produced
by the different MASS libraries are not necessarily bit-wise identical.
422 XL Fortran Enterprise Edition for AIX : User’s Guide