# Ticket #7508(closed defect: fixed)

Opened 4 years ago

## hash collisions for derivatives of symbolic functions - act 3

Reported by: Owned by: burcin burcin major sage-4.3 symbolics pynac N/A Karl-Dieter Crisman Burcin Erocal sage-4.3.rc0

### Description

Reported by Alex Raichev on sage-support:

```----------------------------------------------------------------------
| Sage Version 4.2.1, Release Date: 2009-11-14                       |
| Type notebook() for the GUI, and license() for information.        |
----------------------------------------------------------------------
sage: X= var('x,y,z')
sage: f= function('f',*X); f
f(x, y, z)
sage: d= {}
sage: for l in [1..2]:
....:     for s in UnorderedTuples(X,l):
....:         print diff(f,s)
....:         d[diff(f,s)]= 69
....:
D[0](f)(x, y, z)
D[1](f)(x, y, z)
D[2](f)(x, y, z)
D[0, 0](f)(x, y, z)
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call
last)
...
/Applications/sage/local/lib/python2.6/site-packages/sage/symbolic/
expression_conversions.py in derivative(self, ex, operator)
344             NotImplementedError: derivative
345         """
--> 346         raise NotImplementedError, "derivative"
347
348     def arithmetic(self, ex, operator):

NotImplementedError: derivative
```

This is another form of the problem I couldn't fix in #6243 and #6851.

## Change History

### comment:1 Changed 3 years ago by burcin

• Status changed from new to needs_review
• Report Upstream set to N/A
• Authors set to Burcin Erocal

This is fixed (hopefully, for good) in the new pynac package here:

attachment:trac_7508-fderivative_hash_collision_doctest.patch adds doctests for the fix.

Note that the new pynac version also contains fixes for #7264 and #7406. Tests should be run with the patches from those tickets also applied in this order:

This ticket now depends on #7490.

### comment:2 Changed 3 years ago by kcrisman

• Status changed from needs_review to positive_review

Positive review.

### comment:3 Changed 3 years ago by kcrisman

I should point out that #7264 has a problem, so the spkg should not be merged until that is resolved.

### comment:4 Changed 3 years ago by mhansen

• Status changed from positive_review to closed
• Reviewers set to Karl-Dieter Crisman
• Resolution set to fixed
• Merged in set to sage-4.3.rc0
Note: See TracTickets for help on using tickets.