[CLJ-1336] Allow external collections to use standard collection hashing Created: 31/Jan/14  Updated: 14/Feb/14  Resolved: 14/Feb/14

Status: Closed
Project: Clojure
Component/s: None
Affects Version/s: Release 1.6
Fix Version/s: Release 1.6

Type: Enhancement Priority: Major
Reporter: Alex Miller Assignee: Alex Miller
Resolution: Completed Votes: 0
Labels: None

Attachments: Text File clj-1336-1.patch     Text File clj-1336-2.patch     Text File clj-1336-3.patch     Text File clj-1336-4.patch    
Patch: Code and Test
Approval: Ok


With the change in new hashing algorithms in 1.6, we need to provide a public hook for collections implemented outside of core to participate in the same hash mixing behavior as core collections.

Patch: clj-1336-4.patch
Depends on: CLJ-1338, CLJ-1339, CLJ-1335, CLJ-1331

Comment by Alex Miller [ 04/Feb/14 10:42 AM ]

Updated patch for a couple issues. However, in testing the use of this I discovered that the hash-basis must be an int and the basis accumulation must be based on int-accumulation with int-overflow, so it is not possible to do this in pure Clojure so this function is not currently useful.

I think the best solution would be to provide functions that encapsulate the ordered and unordered algorithms (Murmur3/hashOrdered and Murmur3/hashUnordered basically) such that external collections can implement hasheq correctly and with good performance.

Comment by Alex Miller [ 04/Feb/14 2:45 PM ]

Add new patch that makes Murmur3 class public so it will work for users of mix-collection-hash. Also adds generative tests for comparing the external collection hashing algorithm with hashes produced by internal ordered and unordered collections. These tests currently fail due to CLJ-1335 (empty list and empty lazy seq return wrong hash code).

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