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Problem Report 1602 Details

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Report 1602 Actions

    Problem Report Number 1602
    Submitter's Classification Test Suite problem
    State Resolved
    Resolution Permanent Interpretation (PIN)
    Problem Resolution ID PIN.X.0159
    Raised 1995-02-27 08:00
    Updated 2003-03-13 08:00
    Published 1996-04-01 08:00
    Product Standard Internationalised System Calls and Libraries Extended (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSU version 4.1.0
    Test Identification CAPI.os/genuts/ecvt 4
    Specification System Interfaces and Libraries Issue 4 Version 2
    Location in Spec See Problem Text
    Problem Summary PIN4U.00025 This IR claims that rounding -1.5 to -2 should be allowed.
    Problem Text
    This IR claims that rounding -1.5 to -2 should be allowed.

    Apparently the test case expects that -1.5 should be rounded up
    and that if you are rounding up a negative number, then
    -1.5 would round up to -1, since -1 is larger than -1.5.
    I think the wrong rules for rounding are being used.
    It is true if you are talking about the "ceiling" or "floor"
    of a negative number. In that case if you are rounding up (ceiling)
    -1.5, then you would get -1 and not -2.
    But this is not the formula for rounding a number. If you were
    rounding to the nearest whole number, for example, -1.5 would
    round to -2. This rule works in the same direction as rounding
    to the next nearest digit (rounding to the NSth).
    That is different from "ceiling" or "floor" and independent of
    the floating point rounding mode implemented on the machine.
    I tried this on several interpreters and compilers (where
    rounding the wrong way would not go unnoticed) and found that
    -1.55 rounded to -1.6 and not -1.5.
    For any positive or negative scale point, Ns, I want to "round"
    all real numbers on interval (s/2-abs(Ns)+s/2) to Ns; where N is any
    integer and s is the scaling factor. For the best reference please
    lookup "rounding to the nearest NSth."
    Test Output
    ------------------------------------------------------------------------
    200|0 4 13:20:54|TP Start
    520|0 4 589828 1 1|SPEC1170TESTSUITE CASE 4
    520|0 4 589828 1 2|The low order digit of the string returned by a call
    520|0 4 589828 1 3|to char *ecvt(double value, int ndigit,
    520|0 4 589828 1 4|int *decpt, int *sign) shall be rounded.
    520|0 4 35258381 1 1|TEST: ecvt(0.000000, 1) should return 0
    520|0 4 35258381 1 2|TEST: ecvt(1290000.000000, 3) should return 129
    520|0 4 35258381 1 3|TEST: ecvt(1290000.000000, 2) should return 13
    520|0 4 35258381 1 4|TEST: ecvt(1290000.000000, 1) should return 1
    520|0 4 35258381 1 5|TEST: ecvt(19999999999.000000, 8) should return 20000000
    520|0 4 35258381 1 6|TEST: ecvt(19999990999.000000, 8) should return 19999991
    520|0 4 35258381 1 7|TEST: ecvt(15.499900, 3) should return 155
    520|0 4 35258381 1 8|TEST: ecvt(-2284.347840, 6) should return 228435
    520|0 4 35258381 1 9|TEST: ecvt(-38.293900, 7) should return 3829390
    520|0 4 35258381 1 10|TEST: ecvt(123.450000, 10) should return 1234500000
    520|0 4 35258381 1 11|TEST: ecvt(-123.450000, 3) should return 123
    520|0 4 35258381 1 12|TEST: ecvt(12345.987200, 8) should return 12345997
    520|0 4 35258381 1 13|TEST: ecvt(12345.987300, 8) should return 12345987
    520|0 4 35258381 1 14|TEST: ecvt(0.123460, 8) should return 12345987
    520|0 4 35258381 1 15|TEST: ecvt(0.012346, 8) should return 12345988
    520|0 4 35258381 1 16|TEST: ecvt(-12345.987500, 8) should return 12345987
    520|0 4 35258381 1 17|ERROR: Low order digit is incorrect, expected 12345987, re
    ceived 12345988
    220|0 4 1 13:20:54|FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    We recommend this request be refused.

    We believe the test is correct.

    The value, 1.5, is equidistant between 1 and 2. When 1.5 is
    rounded, it is rounded to 2, the next greater number. The same
    applies to -1.5. It is equidistant between -2 and -1. The same
    rounding rule is applied, and it is rounded to -1, the next greater
    number.

    The references to floor() and ceil() do not apply, because those
    functions do not deal with rounding behavior.

    Although behavior of specific implementaitons is not normative,
    all implementations we have checked PASS this test.

    Review Type Expert Group Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution No Resolution Given
    Review Conclusion
    This is a grey area as the specification does not define rounding.
    A Permanent Interpretation should be granted.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Permanent Interpretation (PIN)
    Review Conclusion
    A Permanent Interpretation is granted.

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