| .Machine {base} | R Documentation |
.Machine is a variable holding information on the numerical
characteristics of the machine R is running on, such as the largest
double or integer and the machine's precision.
.Machine
The algorithm is based on Cody's (1988) subroutine MACHAR.
Note that on most platforms smaller positive values than
.Machine$double.xmin can occur. On a typical R platform the
smallest positive double is about 5e-324.
A list with components (for simplicity, the prefix “double” is omitted in the explanations)
double.eps |
the smallest positive floating-point number
x such that 1 + x != 1. It equals
base^ulp.digits if either base is 2 or rounding
is 0; otherwise, it is (base^ulp.digits) / 2. |
double.neg.eps |
a small positive floating-point number x
such that 1 - x != 1. It equals base^neg.ulp.digits
if base is 2 or round is 0; otherwise, it is
(base^neg.ulp.digits) / 2.
As neg.ulp.digits is bounded below by -(digits + 3),
neg.eps may not be the smallest number that can alter 1 by
subtraction. |
double.xmin |
the smallest non-vanishing normalized
floating-point power of the radix, i.e., base^min.exp. |
double.xmax |
the largest finite floating-point number.
Typically, it is equal to (1 - neg.eps) * base^max.exp, but
on some machines it is only the second, or perhaps third, largest
number, being too small by 1 or 2 units in the last digit of the
significand. |
double.base |
the radix for the floating-point representation |
double.digits |
the number of base digits in the floating-point significand |
double.rounding |
the rounding action. 0 if floating-point addition chops; 1 if floating-point addition rounds, but not in the IEEE style; 2 if floating-point addition rounds in the IEEE style; 3 if floating-point addition chops, and there is partial underflow; 4 if floating-point addition rounds, but not in the IEEE style, and there is partial underflow; 5 if floating-point addition rounds in the IEEE style, and there is partial underflow |
double.guard |
the number of guard digits for multiplication
with truncating arithmetic. It is 1 if floating-point arithmetic
truncates and more than digits base base digits
participate in the post-normalization shift of the floating-point
significand in multiplication, and 0 otherwise. |
double.ulp.digits |
the largest negative integer i such
that 1 + base^i != 1, except that it is bounded below by
-(digits + 3). |
double.neg.ulp.digits |
the largest negative integer i
such that 1 - base^i != 1, except that it is bounded below by
-(digits + 3). |
double.exponent |
the number of bits (decimal places if base is 10) reserved
for the representation of the exponent (including the bias or sign)
of a floating-point number |
double.min.exp |
the largest in magnitude negative integer i such that
base ^ i is positive and normalized. |
double.max.exp |
the smallest positive power of base that overflows. |
integer.max |
the largest integer which can be represented. |
sizeof.long |
the number of bytes in a C long type. |
sizeof.longlong |
the number of bytes in a C long long
type. Will be zero if there is no such type. |
sizeof.longdouble |
the number of bytes in a C long double
type. Will be zero if there is no such type. |
sizeof.pointer |
the number of bytes in a C SEXP
type. |
Cody, W. J. (1988) MACHAR: A subroutine to dynamically determine machine parameters. Transactions on Mathematical Software, 14, 4, 303–311.
.Platform for details of the platform.
.Machine ## or for a neat printout noquote(unlist(format(.Machine)))