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| ID | Category | Severity | Reproducibility | Date Submitted | Last Update | ||||
| 0006601 | [Squeak] Kernel | minor | always | 08-10-07 15:18 | 04-18-10 21:58 | ||||
| Reporter | tween | View Status | public | ||||||
| Assigned To | nicolas cellier | ||||||||
| Priority | normal | Resolution | fixed | ||||||
| Status | closed | Product Version | 3.10 | ||||||
| Summary | 0006601: Float hash incorrect ( 2=2.0 , but 2 hash~=2.0 hash) | ||||||||
| Description |
Since 2 = 2.0 , (2 hash) should equal (2.0 hash). 2 hash -> 2 2.0 hash -> 0 Should the fix be something like this? (in Float>>#hash).. self fractionPart = 0.0 ifTrue:[^self truncated hash]. ^ (((self basicAt: 1) bitAnd: 16r00FFFF00) + ((self basicAt: 2) bitAnd: 16r00FFFF00)) bitShift: -8 |
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SYSTEM WARNING: Creating default object from empty value SYSTEM WARNING: Creating default object from empty value
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Notes |
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(0010971 - 75 - 81 - 81 - 81 - 81 - 81) tween 08-10-07 15:38 |
This seems to have automatically assigned itself to Ken. I don't know why. |
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(0010972 - 149 - 289 - 289 - 289 - 289 - 289) tween 08-10-07 17:48 |
here are some other Number examples... (1/2) = 0.5 -> true (1/2) hash = 0.5 hash -> false 10s0 = 10 -> true 10s0 hash = 10 hash -> false |
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(0010973 - 62 - 62 - 62 - 62 - 62 - 62) KenCausey 08-10-07 19:40 |
It was assigned to me because you failed to choose a category. |
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(0010974 - 176 - 200 - 318 - 318 - 318 - 318) KenCausey 08-10-07 19:41 |
Also, if you have any hope of getting this into 3.10 you will want to add this to http://wiki.squeak.org/squeak/5934 [^] and probably also package it as a .cs.gz with a test. |
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(0010975 - 230 - 242 - 396 - 396 - 396 - 396) tween 08-10-07 20:15 |
It seems that Float hash issues were discussed back in 1997. Also the question of whether 'equal' Objects should _always_ have equal hash values. See the thread started by... http://www.create.ucsb.edu/squeak/9705.html#Letter33 [^] |
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(0011120 - 197 - 221 - 477 - 477 - 477 - 477) nicolas cellier 09-12-07 20:46 edited on: 09-12-07 20:48 |
See also http://bugs.squeak.org/view.php?id=3360 [^] and http://bugs.squeak.org/view.php?id=3374 [^] where you can see nice properties of Smalltalk number equality and draw some conclusions on hash... |
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(0012891 - 1110 - 1420 - 1420 - 1688 - 1688 - 1688) nicolas cellier 01-04-09 22:06 |
I like the proposed fix: self fractionPart = 0.0 ifTrue:[^self truncated hash]. It does not work because Float infinity will raise an Error, but with help of 0006983 : (self isFinite and: [self fractionPart = 0.0]) ifTrue:[^self truncated hash]. That does not spoil efficiency to much, except for large Floats, because they all have fractionPart = 0.0 and will trigger slow LargeInteger algorithms... Is this a problem ? I bet no because huge numbers are very rare... Float allInstances size. "5107" Float allInstances count: [:f | f isFinite and: [f truncated class ~= SmallInteger]]. "33" Then, for fraction we'd better change hash to fit Float like this: | tmp | tmp := self asFloat. tmp isFinite ifTrue: [^tmp hash]. ^numerator hash bitXor: denominator hash And if equality is based on exactness - see 0003374 | tmp | denominator isPowerOfTwo ifTrue: [ "If denominator is not a power of two, I cannot be exactly equal to a Float" tmp := self asFloat. tmp isFinite ifTrue: [^tmp hash]]. ^numerator hash bitXor: denominator hash See 0003374 for changeSet |
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(0012896 - 69 - 117 - 117 - 117 - 117 - 117) nicolas cellier 01-04-09 22:43 |
"fix begin" Installer mantis ensureFix: 3374. "fix test" "fix end" |
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(0013511 - 9 - 9 - 9 - 100 - 100 - 100) nicolas cellier 02-13-10 04:21 |
See 0003374 |
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Issue History |
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| Date Modified | Username | Field | Change |
| 08-10-07 15:18 | tween | New Issue | |
| 08-10-07 15:18 | tween | Status | new => assigned |
| 08-10-07 15:18 | tween | Assigned To | => KenCausey |
| 08-10-07 15:38 | tween | Note Added: 0010971 | |
| 08-10-07 17:48 | tween | Note Added: 0010972 | |
| 08-10-07 19:40 | KenCausey | Note Added: 0010973 | |
| 08-10-07 19:40 | KenCausey | Assigned To | KenCausey => |
| 08-10-07 19:40 | KenCausey | Category | Any => Kernel |
| 08-10-07 19:41 | KenCausey | Note Added: 0010974 | |
| 08-10-07 20:15 | tween | Note Added: 0010975 | |
| 09-12-07 20:46 | nicolas cellier | Note Added: 0011120 | |
| 09-12-07 20:48 | nicolas cellier | Note Edited: 0011120 | |
| 09-25-07 01:13 | matthewf | Relationship added | related to 0003360 |
| 09-25-07 01:13 | matthewf | Relationship added | related to 0003374 |
| 09-25-07 01:15 | matthewf | Status | assigned => new |
| 01-04-09 22:06 | nicolas cellier | Note Added: 0012891 | |
| 01-04-09 22:43 | nicolas cellier | Note Added: 0012896 | |
| 01-10-09 02:00 | Keith_Hodges | Status | new => pending |
| 02-13-10 04:21 | nicolas cellier | Status | pending => resolved |
| 02-13-10 04:21 | nicolas cellier | Fixed in Version | => trunk |
| 02-13-10 04:21 | nicolas cellier | Resolution | open => fixed |
| 02-13-10 04:21 | nicolas cellier | Assigned To | => nicolas cellier |
| 02-13-10 04:21 | nicolas cellier | Note Added: 0013511 | |
| 04-18-10 21:58 | andreas | Status | resolved => closed |
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