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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] [Closed] (MATH-499) FastMath nextAfter(double,double) bugs with special doubles
Date Wed, 23 Mar 2011 20:39:05 GMT

     [ https://issues.apache.org/jira/browse/MATH-499?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Luc Maisonobe closed MATH-499.
------------------------------


Closing issue as it was included in version 2.2, which has been released

> FastMath nextAfter(double,double) bugs with special doubles
> -----------------------------------------------------------
>
>                 Key: MATH-499
>                 URL: https://issues.apache.org/jira/browse/MATH-499
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 2.2, 3.0
>         Environment: Java 1.6
>            Reporter: Sebb
>            Assignee: Sebb
>             Fix For: 2.2, 3.0
>
>
> nextAfter(double, double) is added in StrictMath 1.6, so one needs to test with Java
1.6 to see thi.
> There are various boundary errors with nextAfter(double, double) - see below.
> I think these are partially due to missing checks for special cases (e.g. the NaNs),
and partially due to the following code:
> {code}
> if (d * (direction - d) >= 0) {
> // we should increase the mantissa
> {code}
> This appears to be a shorthand for something like:
> {code}
> if (((d >=0) && (direction >= d)) || ((d<0) && (direction <0)))
{
> // we should increase the mantissa
> {code}
> however the expression (direction - d) overlows for some double values, thus causing
the wrong branch to be taken.
> double nextAfter(-0.0, -0.0) expected -0.0 actual 4.9E-324 entries [1, 1]
> double nextAfter(-0.0, 0.0) expected 0.0 actual 4.9E-324 entries [1, 2]
> double nextAfter(-0.0, NaN) expected NaN actual 4.9E-324 entries [1, 3]
> double nextAfter(0.0, -0.0) expected -0.0 actual 4.9E-324 entries [2, 1]
> double nextAfter(0.0, 0.0) expected 0.0 actual 4.9E-324 entries [2, 2]
> double nextAfter(0.0, NaN) expected NaN actual 4.9E-324 entries [2, 3]
> double nextAfter(-Infinity, NaN) expected NaN actual -Infinity entries [4, 3]
> double nextAfter(Infinity, NaN) expected NaN actual Infinity entries [5, 3]
> double nextAfter(-1.7976931348623157E308, NaN) expected NaN actual -1.7976931348623155E308
entries [6, 3]
> double nextAfter(1.7976931348623157E308, NaN) expected NaN actual 1.7976931348623155E308
entries [7, 3]
> double nextAfter(-1.1102230246251565E-16, NaN) expected NaN actual -1.1102230246251564E-16
entries [8, 3]
> double nextAfter(1.1102230246251565E-16, NaN) expected NaN actual 1.1102230246251564E-16
entries [9, 3]
> double nextAfter(-2.2250738585072014E-308, -0.0) expected -2.225073858507201E-308 actual
-2.225073858507202E-308 entries [10, 1]
> double nextAfter(-2.2250738585072014E-308, 0.0) expected -2.225073858507201E-308 actual
-2.225073858507202E-308 entries [10, 2]
> double nextAfter(-2.2250738585072014E-308, NaN) expected NaN actual -2.225073858507201E-308
entries [10, 3]
> double nextAfter(-2.2250738585072014E-308, 1.1102230246251565E-16) expected -2.225073858507201E-308
actual -2.225073858507202E-308 entries [10, 9]
> double nextAfter(-2.2250738585072014E-308, 2.2250738585072014E-308) expected -2.225073858507201E-308
actual -2.225073858507202E-308 entries [10, 11]
> double nextAfter(-2.2250738585072014E-308, -4.9E-324) expected -2.225073858507201E-308
actual -2.225073858507202E-308 entries [10, 12]
> double nextAfter(-2.2250738585072014E-308, 4.9E-324) expected -2.225073858507201E-308
actual -2.225073858507202E-308 entries [10, 13]
> double nextAfter(2.2250738585072014E-308, -0.0) expected 2.225073858507201E-308 actual
2.225073858507202E-308 entries [11, 1]
> double nextAfter(2.2250738585072014E-308, 0.0) expected 2.225073858507201E-308 actual
2.225073858507202E-308 entries [11, 2]
> double nextAfter(2.2250738585072014E-308, NaN) expected NaN actual 2.225073858507201E-308
entries [11, 3]
> double nextAfter(2.2250738585072014E-308, -1.1102230246251565E-16) expected 2.225073858507201E-308
actual 2.225073858507202E-308 entries [11, 8]
> double nextAfter(2.2250738585072014E-308, -2.2250738585072014E-308) expected 2.225073858507201E-308
actual 2.225073858507202E-308 entries [11, 10]
> double nextAfter(2.2250738585072014E-308, -4.9E-324) expected 2.225073858507201E-308
actual 2.225073858507202E-308 entries [11, 12]
> double nextAfter(2.2250738585072014E-308, 4.9E-324) expected 2.225073858507201E-308 actual
2.225073858507202E-308 entries [11, 13]
> double nextAfter(-4.9E-324, -0.0) expected -0.0 actual -1.0E-323 entries [12, 1]
> double nextAfter(-4.9E-324, 0.0) expected -0.0 actual -1.0E-323 entries [12, 2]
> double nextAfter(-4.9E-324, NaN) expected NaN actual -0.0 entries [12, 3]
> double nextAfter(-4.9E-324, 1.1102230246251565E-16) expected -0.0 actual -1.0E-323 entries
[12, 9]
> double nextAfter(-4.9E-324, 2.2250738585072014E-308) expected -0.0 actual -1.0E-323 entries
[12, 11]
> double nextAfter(-4.9E-324, 4.9E-324) expected -0.0 actual -1.0E-323 entries [12, 13]
> double nextAfter(4.9E-324, -0.0) expected 0.0 actual 1.0E-323 entries [13, 1]
> double nextAfter(4.9E-324, 0.0) expected 0.0 actual 1.0E-323 entries [13, 2]
> double nextAfter(4.9E-324, NaN) expected NaN actual 0.0 entries [13, 3]
> double nextAfter(4.9E-324, -1.1102230246251565E-16) expected 0.0 actual 1.0E-323 entries
[13, 8]
> double nextAfter(4.9E-324, -2.2250738585072014E-308) expected 0.0 actual 1.0E-323 entries
[13, 10]
> double nextAfter(4.9E-324, -4.9E-324) expected 0.0 actual 1.0E-323 entries [13, 12]

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