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From "Leo Li (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-329) Endless loop when using Double.parseDouble(String) with certain types of value
Date Thu, 23 Nov 2006 08:26:07 GMT
    [ http://issues.apache.org/jira/browse/HARMONY-329?page=comments#action_12452169 ] 
            
Leo Li commented on HARMONY-329:
--------------------------------

It is a fault of the algorithm in the math lab used by harmony.
In the file  trunk/modules/luni/src/main/native/luni/shared/dblparse.c
there is a comment of function doubleAlgorithm:
/* The algorithm for the function doubleAlgorithm() below can be found
 * in:
 *
 *      "How to Read Floating-Point Numbers Accurately", William D.
 *      Clinger, Proceedings of the ACM SIGPLAN '90 Conference on
 *      Programming Language Design and Implementation, June 20-22,
 *      1990, pp. 92-101.
 *
 * There is a possibility that the function will end up in an endless
 * loop if the given approximating floating-point number (a very small
 * floating-point whose value is very close to zero) straddles between
 * two approximating integer values. We modified the algorithm slightly
 * to detect the case where it oscillates back and forth between
 * incrementing and decrementing the floating-point approximation. It
 * is currently set such that if the oscillation occurs more than twice
 * then return the original approximation.
 */

It seems that it will fail in endless loop in the testcase.
Any suggestion?


> Endless loop when using Double.parseDouble(String) with certain types of value
> ------------------------------------------------------------------------------
>
>                 Key: HARMONY-329
>                 URL: http://issues.apache.org/jira/browse/HARMONY-329
>             Project: Harmony
>          Issue Type: Bug
>          Components: Classlib
>            Reporter: Sian January
>
> Calling Double.parseDouble(..) with certain Strings (e.g. Double.parseDouble("-1.233999999999999965116738099630936817275852021384209929081813042837802886790127428328465579708849276001782791006814286802871737087810957327493372866733334925806221045495205250590286471187577636646208155890426896101636282423463443661040209738873506655844025580428394216030152374941053494694642722606658935546875E-112");)
causes an endless loop.  
> Although this is not necessarily a case you would see in regular programming it happens
when you do something like new BigDecimal(-1.234E-112).doubleValue(), which was the cause
of the endless loop mentioned in HARMONY-319.
> The loop occurs in the native method "doubleAlgorithm (JNIEnv * env, U_64 * f, IDATA
length, jint e, jdouble z)" in native-src/shared/math/dblparse.c.

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