Mercurial > cpython-lru_cache-weakref

annotate Lib/test/test_complex.py @ 17322:bd110eadc19a legacy-trunk

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One-liner critical fix from Jim Fulton: Eric's string-method crusade got the order backwards in a line (for .find()).
author Tim Peters <tim.peters@gmail.com>
date Thu, 05 Apr 2001 22:26:23 +0000
parents 2c1be7924b04
children 64e1ea34b553
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
17066
2c1be7924b04 SF bug [ #409448 ] Complex division is braindead
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1 from test_support import TestFailed
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2 from random import random
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3
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4 # XXX need many, many more tests here.
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5
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6 nerrors = 0
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7
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8 def check_close_real(x, y, eps=1e-12):
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9 """Return true iff floats x and y "are close\""""
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10 # put the one with larger magnitude second
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11 if abs(x) > abs(y):
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12 x, y = y, x
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13 if y == 0:
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14 return abs(x) < eps
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15 if x == 0:
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16 return abs(y) < eps
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17 # check that relative difference < eps
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18 return abs((x-y)/y) < eps
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19
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20 def check_close(x, y, eps=1e-12):
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21 """Return true iff complexes x and y "are close\""""
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22 return check_close_real(x.real, y.real, eps) and \
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23 check_close_real(x.imag, y.imag, eps)
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24
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25 def test_div(x, y):
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26 """Compute complex z=x*y, and check that z/x==y and z/y==x."""
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27 global nerrors
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28 z = x * y
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29 if x != 0:
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30 q = z / x
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31 if not check_close(q, y):
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32 nerrors += 1
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33 print `z`, "/", `x`, "==", `q`, "but expected", `y`
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34 if y != 0:
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35 q = z / y
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36 if not check_close(q, x):
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37 nerrors += 1
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38 print `z`, "/", `y`, "==", `q`, "but expected", `x`
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39
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40 simple_real = [float(i) for i in range(-5, 6)]
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41 simple_complex = [complex(x, y) for x in simple_real for y in simple_real]
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42 for x in simple_complex:
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43 for y in simple_complex:
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44 test_div(x, y)
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45
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46 # A naive complex division algorithm (such as in 2.0) is very prone to
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47 # nonsense errors for these (overflows and underflows).
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48 test_div(complex(1e200, 1e200), 1+0j)
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49 test_div(complex(1e-200, 1e-200), 1+0j)
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50
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51 # Just for fun.
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52 for i in range(100):
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53 test_div(complex(random(), random()),
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54 complex(random(), random()))
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55
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56 try:
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57 z = 1.0 / (0+0j)
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58 except ZeroDivisionError:
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59 pass
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60 else:
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61 nerrors += 1
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62 raise TestFailed("Division by complex 0 didn't raise ZeroDivisionError")
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63
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64 if nerrors:
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65 raise TestFailed("%d tests failed" % nerrors)