[Simulavr-devel] [bug #47629] adc_diff_t25 tests 00 and 02 fail on 64bit Ubuntu 14.04

[anonymous]

URL:
  <http://savannah.nongnu.org/bugs/?47629>

                 Summary: adc_diff_t25 tests 00 and 02 fail on 64bit Ubuntu
14.04
                 Project: Simulavr: an AVR simulator
            Submitted by: None
            Submitted on: Втр 05 Апр 2016 20:38:41
                Category: Test Suite
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
       Component Version: simulavr

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Details:

Simulavr version: rel-1.1 branch (commit: 4d3c8c0fae3efa95)

Test suite fails on 64bit Ubuntu 14.04 with following errors:


======================================================================
FAIL: test_00 (adc_diff_t25.TestCase)
adc_diff_t25_attiny25::check adc conversion, differential channel, bipolar
mode
----------------------------------------------------------------------
Traceback (most recent call last):
  File "adc_diff_t25.py", line 83, in test_00
    self.assertValue(0.8, 1.0, 2.56, False)
  File "adc_diff_t25.py", line 52, in assertValue
    self.assertEqual(v, e, "expected adc value is 0x%x, got 0x%x" % (e, v))
AssertionError: expected adc value is 0x3d9, got 0x3d8

======================================================================
FAIL: test_02 (adc_diff_t25.TestCase)
adc_diff_t25_attiny25::check adc conversion, differential channel, unipolar
mode with IPR
----------------------------------------------------------------------
Traceback (most recent call last):
  File "adc_diff_t25.py", line 147, in test_02
    self.assertValue(1.0, 0.8, 2.56)
  File "adc_diff_t25.py", line 52, in assertValue
    self.assertEqual(v, e, "expected adc value is 0x%x, got 0x%x" % (e, v))
AssertionError: expected adc value is 0x4f, got 0x50



== Environment ==


Ubuntu 14.04.4 LTS (GNU/Linux 4.2.0-27-generic x86_64)

$ uname -a
Linux ubuntu64 4.2.0-27-generic #32~14.04.1-Ubuntu SMP Fri Jan 22 15:32:26 UTC
2016 x86_64 x86_64 x86_64 GNU/Linux

$ gcc --version
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4

$ python --version
Python 2.7.6



== Investigation ==

Floating point calculations give slightly different result in C++ Simulavr
code and in Python tests. And after truncation of the fractional part, integer
results differ by 1.

The code from adc_diff_t25.py:


  def assertValue(self, pValue, nValue, refValue, unipolar = True):
    if unipolar:
      rng = 1024
    else:
      rng = 512
    v = self.sim.getWordByName(self.dev, "adc_value")
    e = int(((pValue - nValue) / refValue) * rng) & 0x3ff
    self.assertEqual(v, e, "expected adc value is 0x%x, got 0x%x" % (e, v))


Failure in test_00 is caused by following values:

v = 984
((pValue - nValue) / refValue) * rng = -39.9999999999999929 (after truncation
to int becomes -39 and not -40)


Failure in test_02 is caused by following values:

v = 80
((pValue - nValue) / refValue) * rng = 79.9999999999999858 (after truncation
to int becomes 79 and not 80)


Probably, the behavior described here takes place:
[http://www.viva64.com/en/b/0074/]


== Solution ==

Test voltage value(s) should be adjusted to produce a more stable result (I've
changed 0.8 to 0.79999).

The patch attached.


Best regards,
Igor A. Perminov



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File Attachments:


-------------------------------------------------------
Date: Втр 05 Апр 2016 20:38:41  Name: fix_regress_amd64.patch  Size: 1kB
  By: None

<http://savannah.nongnu.org/bugs/download.php?file_id=36843>

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