Wolfram Language Paclet Repository
Community-contributed installable additions to the Wolfram Language
JasonB`WeakCache`
WeakHashTable  |
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Details and Options
Examples
(7)
Basic Examples
(1)
As in many examples for this paclet, we set to zero to avoid leaving strong references to expressions in the session history:
In[1]:=
$HistoryLength=0
Out[1]=
0
Create a new table and an expression:
In[2]:=
table=
["example table 1"]
 | WeakHashTable |
Out[2]=
WeakHashTable
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In[3]:=
expr=RandomImage[4]
Out[3]=
Perform some expensive computation that you wish to cache:
In[4]:=
(data=ImageKeypoints[expr])//Shallow//RepeatedTiming
Out[4]=
{0.00525441,{{88.1816,77.1035},{21.5787,75.5165},{34.8592,15.4442},{94.7895,109.767},{22.5318,15.3431},{49.9019,37.2992},{114.659,79.3872},{58.3214,63.6881},{58.3328,31.0274},{66.9111,97.8033},87}}
Add the data to the table:
In[5]:=
table["Insert",expr,"key",data]
In the above we use as the key - any expression can be used as a key, but using simple expressions like strings or symbols is best for efficiency. Verify that the data in the table is the same and that retrieving it is fast:
"key"
In[6]:=
SameQ[data,table["Lookup",expr,"key"]]//RepeatedTiming
Out[6]=
{3.12678×,True}
-6
10
Since the history is turned off is the only reference to the image expression, deleting it will clear the table:
expr
In[7]:=
table["Length"]
Out[7]=
1
In[8]:=
expr=.
In[9]:=
table["Length"]
Out[9]=
0
In[10]:=
table["Lookup",expr,"key"]
Out[10]=
$Failed
Scope
(1)
Generalizations & Extensions
(1)
Possible Issues
(4)
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