iMachine

Returns integer information describing the computer’s arithmetic.

Synopsis

iMachine (n)

Required Arguments

int n (Input)

Index indicating which value is to be returned. It must be between 0 and 12.

Return Value

The requested value is returned. If n is out of range, NaN is returned.

Description

Function iMachine returns information describing the computer’s arithmetic. This can be used to make programs machine independent.

iMachine(0) = Number of bits per byte

Assume that integers are represented in M-digit, base-A form as

$$\sigma \sum_{k=0}^{M} x_k A^k$$

where σ is the sign and $0\leq x_k<A$ for $k=0,\ldots,M$. Then,

n	Definition
0	C, bits per character
1	A, the base
2	$M_s$, the number of base-A digits in a short int
3	$A^{M_S}-1$, the largest short int
4	$M_1$ the number of base-A digits in a long int
5	$A^{M_l}-1$, the largest long int

Assume that floating-point numbers are represented in N-digit, base B form as

$$\sigma B^E \sum_{k=1}^{N} x_k B^{-k}$$

where σ is the sign and $0\leq x_k<B$ for $k=1,\ldots,N$ and $E_{min}\leq E\leq E_{max}$. Then

n	Definition
6	B, the base
7	$N_f$, the number of base-B digits in float
8	${E}_{\mathrm{min}_f}$, the smallest float exponent
9	${E}_{\mathrm{max}_f}$, the largest float exponent
10	$N_d$, the number of base-B digits in double
11	${E}_{\mathrm{max}_f}$, the largest long int
12	${E}_{\mathrm{max}_d}$, the number of base-B digits in double

Example

In this example, all the values returned by iMachine on a 32‑bit machine with IEEE (Institute for Electrical and Electronics Engineer) arithmetic are printed.

from __future__ import print_function
from pyimsl.stat.iMachine import iMachine

for n in range(0, 13):
    ans = iMachine(n)
    print("iMachine[", n, "] = ", ans)

Output

iMachine[ 0 ] =  8
iMachine[ 1 ] =  2
iMachine[ 2 ] =  15
iMachine[ 3 ] =  32767
iMachine[ 4 ] =  63
iMachine[ 5 ] =  9223372036854775807
iMachine[ 6 ] =  2
iMachine[ 7 ] =  24
iMachine[ 8 ] =  -125
iMachine[ 9 ] =  128
iMachine[ 10 ] =  53
iMachine[ 11 ] =  -1021
iMachine[ 12 ] =  1024