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comparison dep/fmt/support/compute-powers.py @ 343:1faa72660932

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*: transfer back to cmake from autotools autotools just made lots of things more complicated than they should have and many things broke (i.e. translations)
author Paper <paper@paper.us.eu.org>
date Thu, 20 Jun 2024 05:56:06 -0400
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342:adb79bdde329 343:1faa72660932
1 #!/usr/bin/env python
2 # Compute 10 ** exp with exp in the range [min_exponent, max_exponent] and print
3 # normalized (with most-significant bit equal to 1) significands in hexadecimal.
4
5 from __future__ import print_function
6
7 min_exponent = -348
8 max_exponent = 340
9 step = 8
10 significand_size = 64
11 exp_offset = 2000
12
13 class fp:
14 pass
15
16 powers = []
17 for i, exp in enumerate(range(min_exponent, max_exponent + 1, step)):
18 result = fp()
19 n = 10 ** exp if exp >= 0 else 2 ** exp_offset / 10 ** -exp
20 k = significand_size + 1
21 # Convert to binary and round.
22 binary = '{:b}'.format(n)
23 result.f = (int('{:0<{}}'.format(binary[:k], k), 2) + 1) / 2
24 result.e = len(binary) - (exp_offset if exp < 0 else 0) - significand_size
25 powers.append(result)
26 # Sanity check.
27 exp_offset10 = 400
28 actual = result.f * 10 ** exp_offset10
29 if result.e > 0:
30 actual *= 2 ** result.e
31 else:
32 for j in range(-result.e):
33 actual /= 2
34 expected = 10 ** (exp_offset10 + exp)
35 precision = len('{}'.format(expected)) - len('{}'.format(actual - expected))
36 if precision < 19:
37 print('low precision:', precision)
38 exit(1)
39
40 print('Significands:', end='')
41 for i, fp in enumerate(powers):
42 if i % 3 == 0:
43 print(end='\n ')
44 print(' {:0<#16x}'.format(fp.f, ), end=',')
45
46 print('\n\nExponents:', end='')
47 for i, fp in enumerate(powers):
48 if i % 11 == 0:
49 print(end='\n ')
50 print(' {:5}'.format(fp.e), end=',')
51
52 print('\n\nMax exponent difference:',
53 max([x.e - powers[i - 1].e for i, x in enumerate(powers)][1:]))