Fwd: JDK 9 RFR of JDK-8030942: Explicitly state floating-point summation requirements on non-finite inputs

Georgiy Rakov georgiy.rakov at oracle.com
Fri Jul 18 19:00:50 UTC 2014


On 18.07.2014 20:14, Joe Darcy wrote:
> Hello Georgiy,
>
> On 07/18/2014 05:29 AM, Georgiy Rakov wrote:
>> Hello Joe,
>>
>> could you please clarify by short example following assertion:
>>
>>   154      * If the exact sum is infinite, a properly-signed infinity is
>>   155      * returned.
>>
>> I'm afraid I don't quite understand what you mean here by 'exact sum'.
>
> By "exact sum," the sum absent any floating-point rounding, the sum 
> you would get using infinite precision to operate on the values in 
> question.
>
> The sentence in question is intended to be a short way of saying "If 
> you have same-signed infinities in your input, the result will be an 
> infinity of that sign." In particular, this disallows the behavior 
> that was fixed before JDK 8 GA where having infinities in the input 
> would cause a NaN to be returned because of how the compensated 
> summation code manipulated those values.
>
Thanks, I see,
however it seems to me a bit confusing, since the term "infinite exact 
sum" seems to me not obvious and I believe it needs some definition. I'd 
like to suggest to use more straightforward approach, that is as you've 
said: "If you have same-signed infinities in your input, the result will 
be an infinity of that sign.". I believe it would be more clear for end 
user (at least for me :)) and from conformance point of view.

Besides it seems to me a bit questionable. For instance "inexact some" 
looks like more appropriate, since overflowing to infinity occurs when 
_actual _sum exceeds the limit. By actual sum I mean sum resulted from 
actual summation with all the rounding happened. There wouldn't be such 
questions, provided straightforward approach is used.

Thanks,
Georgiy.

> HTH,
>
> -Joe
>
>>
>> Thank you,
>> Georgiy.
>>
>> On 16.07.2014 16:37, Paul Sandoz wrote:
>>>
>>>
>>> Begin forwarded message:
>>>
>>>> *From: *Joe Darcy <joe.darcy at oracle.com <mailto:joe.darcy at oracle.com>>
>>>> *Subject: **JDK 9 RFR of JDK-8030942: Explicitly state 
>>>> floating-point summation requirements on non-finite inputs*
>>>> *Date: *July 16, 2014 2:29:46 AM GMT+02:00
>>>> *To: *Core-Libs-Dev <core-libs-dev at openjdk.java.net 
>>>> <mailto:core-libs-dev at openjdk.java.net>>
>>>>
>>>> Hello,
>>>>
>>>> Please review my changes to address:
>>>>
>>>>    JDK-8030942: Explicitly state floating-point summation 
>>>> requirements on non-finite inputs
>>>> http://cr.openjdk.java.net/~darcy/8030942.0/ 
>>>> <http://cr.openjdk.java.net/%7Edarcy/8030942.0/>
>>>>
>>>> Patch below.
>>>>
>>>> Thanks,
>>>>
>>>> -Joe
>>>>
>>>> --- old/src/share/classes/java/util/DoubleSummaryStatistics.java 
>>>> 2014-07-15 17:26:41.000000000 -0700
>>>> +++ new/src/share/classes/java/util/DoubleSummaryStatistics.java 
>>>> 2014-07-15 17:26:41.000000000 -0700
>>>> @@ -1,5 +1,5 @@
>>>> /*
>>>> - * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All 
>>>> rights reserved.
>>>> + * Copyright (c) 2012, 2014, Oracle and/or its affiliates. All 
>>>> rights reserved.
>>>>  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
>>>>  *
>>>>  * This code is free software; you can redistribute it and/or modify it
>>>> @@ -129,9 +129,6 @@
>>>>      * Returns the sum of values recorded, or zero if no values 
>>>> have been
>>>>      * recorded.
>>>>      *
>>>> -     * If any recorded value is a NaN or the sum is at any point a NaN
>>>> -     * then the sum will be NaN.
>>>> -     *
>>>>      * <p> The value of a floating-point sum is a function both of the
>>>>      * input values as well as the order of addition operations. The
>>>>      * order of addition operations of this method is intentionally
>>>> @@ -143,6 +140,23 @@
>>>>      * numerical sum compared to a simple summation of {@code double}
>>>>      * values.
>>>>      *
>>>> +     * <p>If any recorded value is a NaN or the intermediate sum is at
>>>> +     * any point a NaN, then the final sum will be NaN.
>>>> +     *
>>>> +     * If the recorded values contain infinities of opposite sign, the
>>>> +     * final sum will be NaN.
>>>> +     *
>>>> +     * It is possible for intermediate sums of finite values to
>>>> +     * overflow into opposite-signed infinities; if that occurs, the
>>>> +     * final sum will be NaN even if the recorded values are all
>>>> +     * finite.
>>>> +     *
>>>> +     * If the exact sum is infinite, a properly-signed infinity is
>>>> +     * returned.
>>>> +     *
>>>> +     * If all the recorded values are zero, the sign of zero is
>>>> +     * <em>not</em> guaranteed to be preserved in the final sum.
>>>> +     *
>>>>      * @apiNote Values sorted by increasing absolute magnitude tend 
>>>> to yield
>>>>      * more accurate results.
>>>>      *
>>>> @@ -193,9 +207,6 @@
>>>>      * Returns the arithmetic mean of values recorded, or zero if no
>>>>      * values have been recorded.
>>>>      *
>>>> -     * If any recorded value is a NaN or the sum is at any point a NaN
>>>> -     * then the average will be code NaN.
>>>> -     *
>>>>      * <p>The average returned can vary depending upon the order in
>>>>      * which values are recorded.
>>>>      *
>>>> @@ -203,6 +214,10 @@
>>>>      * other technique to reduce the error bound in the {@link #getSum
>>>>      * numerical sum} used to compute the average.
>>>>      *
>>>> +     * <p>This method can return a NaN or infinite result in the same
>>>> +     * kind of numerical situations as {@linkplain #getSum() the sum}
>>>> +     * can be NaN or infinite, respectively.
>>>> +     *
>>>>      * @apiNote Values sorted by increasing absolute magnitude tend 
>>>> to yield
>>>>      * more accurate results.
>>>>      *
>>>> --- old/src/share/classes/java/util/stream/DoubleStream.java 
>>>> 2014-07-15 17:26:42.000000000 -0700
>>>> +++ new/src/share/classes/java/util/stream/DoubleStream.java 
>>>> 2014-07-15 17:26:42.000000000 -0700
>>>> @@ -1,5 +1,5 @@
>>>> /*
>>>> - * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All 
>>>> rights reserved.
>>>> + * Copyright (c) 2012, 2014, Oracle and/or its affiliates. All 
>>>> rights reserved.
>>>>  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
>>>>  *
>>>>  * This code is free software; you can redistribute it and/or modify it
>>>> @@ -470,10 +470,7 @@
>>>>      * code is not necessarily equivalent to the summation computation
>>>>      * done by this method.
>>>>      *
>>>> -     * <p>If any stream element is a NaN or the sum is at any 
>>>> point a NaN
>>>> -     * then the sum will be NaN.
>>>> -     *
>>>> -     * The value of a floating-point sum is a function both
>>>> +     * <p>The value of a floating-point sum is a function both
>>>>      * of the input values as well as the order of addition
>>>>      * operations. The order of addition operations of this method is
>>>>      * intentionally not defined to allow for implementation
>>>> @@ -485,6 +482,23 @@
>>>>      * numerical sum compared to a simple summation of {@code double}
>>>>      * values.
>>>>      *
>>>> +     * <p>If any stream element is a NaN or the intermediate sum is at
>>>> +     * any point a NaN, then the final sum will be NaN.
>>>> +     *
>>>> +     * If the stream elements contain infinities of opposite sign, the
>>>> +     * final sum will be NaN.
>>>> +     *
>>>> +     * It is possible for intermediate sums of finite values to
>>>> +     * overflow into opposite-signed infinities; if that occurs, the
>>>> +     * final sum will be NaN even if the stream elements are all
>>>> +     * finite.
>>>> +     *
>>>> +     * If the exact sum is infinite, a properly-signed infinity is
>>>> +     * returned.
>>>> +     *
>>>> +     * If all the stream elements are zero, the sign of zero is
>>>> +     * <em>not</em> guaranteed to be preserved in the final sum.
>>>> +     *
>>>>      * <p>This is a <a href="package-summary.html#StreamOps">terminal
>>>>      * operation</a>.
>>>>      *
>>>> @@ -555,9 +569,6 @@
>>>>      * mean of elements of this stream, or an empty optional if this
>>>>      * stream is empty.
>>>>      *
>>>> -     * If any recorded value is a NaN or the sum is at any point a NaN
>>>> -     * then the average will be NaN.
>>>> -     *
>>>>      * <p>The average returned can vary depending upon the order in
>>>>      * which values are recorded.
>>>>      *
>>>> @@ -565,6 +576,10 @@
>>>>      * other technique to reduce the error bound in the {@link #sum
>>>>      * numerical sum} used to compute the average.
>>>>      *
>>>> +     * <p>This method can return a NaN or infinite result in the same
>>>> +     * kind of numerical situations as {@linkplain #sum() the sum} can
>>>> +     * be NaN or infinite, respectively.
>>>> +     *
>>>>      *  <p>The average is a special case of a <a
>>>>      * href="package-summary.html#Reduction">reduction</a>.
>>>>      *
>>>>
>>>
>>
>




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