LookupTable working very slow..

[gsharma84]

Hi,
I just wanted to enquire, does lookup table has any limitation as to the number of entries it can take and work efficiently?
We use it in one of our apps and the entries in lookup table increase to about 7-8K; when I inspect on the variable holding the lookup table, the image simply clocks.

[marten]

This class works with SmallInteger hash values, AbtHighCapacityLookupTable works with 32-Bit hash values .... therefore try to use the latter class.

[gsharma84]

thanks ! but would this 'AbtHighCapacityLookupTable' work the same wasy as LookupTable use to work for a smaller table. My concern is the performance for LookupTable with lesser entries, hope that would not be degraded...

[daswartz]

thanks ! but would this 'AbtHighCapacityLookupTable' work the same way as LookupTable use to work for a smaller table. My concern is the performance for LookupTable with lesser entries, hope that would not be degraded...

AbtHighCapacityLookupTable is somewhat slower than LookupTable, because abtHash32 is generally slower than hash. Of course the difference depends greatly on what you are hashing. Here's an example using reltively short strings for keys and doing five million lookups on both types of lookup tables with five hundred entries. The following code:

Code: Select all

|tbl bigtbl rand keys|
tbl := LookupTable new: 200.
bigtbl := AbtHighCapacityLookupTable new: 200.
rand := EsRandom new.
500 timesRepeat:
   [|r|
   r := rand next.
   tbl at: r printString put: r.
   bigtbl at: r printString put: r].
keys := tbl keys.
Transcript cr.
Transcript show: (Time millisecondsToRun:
   [10000 timesRepeat: [keys do: [:each | tbl at: each]]]) printString.
Transcript cr.
Transcript show: (Time millisecondsToRun:
   [10000 timesRepeat: [keys do: [:each | bigtbl at: each]]]) printString.

runs right around 2.5 seconds for the LookupTable and 3.1 seconds for the AbtHighCapacityLookupTable on my relatively old laptop.

I always use AbtHighCapacityLookupTable if my table will exceed about 12000 entries.

Doug swartz

[gsharma84]

thanks Doug swartz, this is really very helpfull..!!
However, this raises another question, is there any limit beyond which we should use abtHighCapacityLookupTable & not LookupTable? Do we have a parameter for defining when to use a LookupTable & when to an AbtHighCapacityLookupTable?

[a62754]

I feel there should be automatic transformation from a lookup table to a high capacity table by smalltalk vm - just like smallints get transformed into integers.

[gsharma84]

Hi,
I'm noticing a similar issue with the Dictionary class as well. The entries in the dictionary are about 50K+ and to simply do,
"dictionary keysDo: [ :each| each ]" it takes more than a minute...

[PhotonDemon]

Hi,

The AbtHighCapacityDictionary for the same reason posted above.

Lou