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Posted to notifications@asterixdb.apache.org by "Taewoo Kim (JIRA)" <ji...@apache.org> on 2017/02/01 06:10:51 UTC
[jira] [Updated] (ASTERIXDB-1778) Calculating the edit-distance in
SimilarityMetricEditDistance class can be improved.
[ https://issues.apache.org/jira/browse/ASTERIXDB-1778?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Taewoo Kim updated ASTERIXDB-1778:
----------------------------------
Description:
Local optimization of the current edit-distance handling code in AsterixDB: Can we terminate the edit distance calculation based on a given edit-distance threshold T? I think the answer is yes.
Basic Algorithm:
For two strings X and Y,
Init:
Construct D(len(X)+1=M, len(Y)+1=N).
D(i,0) = i
D(j,0) = j
Iteration:
{code}
For each i = 1 to M
For each j = 1 to N
D(i,j) = min( D(i-1,j) + 1 // deletion case
D(i,j-1) + 1 // insertion case
D(i-1,j-1) + cost (cost is 2 if X(i) != Y(j),
cost is 0 if X(i) = Y(j))
)
{code}
Result:
D(M,N) is the edit distance value.
Example:
Early Termination condition:
So, for the given threshold T, we can stop the computation early if the values of three cases are greater than T. That is,
min (D(i-1,j), D(i,j-1), D(i-1,j-1)) > T
This holds since if the cost of all possible cases (insertion, deletion, and substitution) is greater than T, all future operations will be greater than T in any cases.
was:
Local optimization of the current edit-distance handling code in AsterixDB: Can we terminate the edit distance calculation based on a given edit-distance threshold T? I think the answer is yes.
Basic Algorithm:
For two strings X and Y,
Init:
Construct D(len(X)+1=M, len(Y)+1=N).
D(i,0) = i
D(j,0) = j
Iteration:
For each i = 1 to M
For each j = 1 to N
D(i,j) = min( D(i-1,j) + 1 // deletion case
D(i,j-1) + 1 // insertion case
D(i-1,j-1) + cost (cost is 2 if X(i) != Y(j),
cost is 0 if X(i) = Y(j))
)
Result:
D(M,N) is the edit distance value.
Example:
Early Termination condition:
So, for the given threshold T, we can stop the computation early if the values of three cases are greater than T. That is,
min (D(i-1,j), D(i,j-1), D(i-1,j-1)) > T
This holds since if the cost of all possible cases (insertion, deletion, and substitution) is greater than T, all future operations will be greater than T in any cases.
> Calculating the edit-distance in SimilarityMetricEditDistance class can be improved.
> ------------------------------------------------------------------------------------
>
> Key: ASTERIXDB-1778
> URL: https://issues.apache.org/jira/browse/ASTERIXDB-1778
> Project: Apache AsterixDB
> Issue Type: Improvement
> Reporter: Taewoo Kim
> Priority: Minor
>
> Local optimization of the current edit-distance handling code in AsterixDB: Can we terminate the edit distance calculation based on a given edit-distance threshold T? I think the answer is yes.
> Basic Algorithm:
> For two strings X and Y,
> Init:
> Construct D(len(X)+1=M, len(Y)+1=N).
> D(i,0) = i
> D(j,0) = j
> Iteration:
> {code}
> For each i = 1 to M
> For each j = 1 to N
> D(i,j) = min( D(i-1,j) + 1 // deletion case
> D(i,j-1) + 1 // insertion case
> D(i-1,j-1) + cost (cost is 2 if X(i) != Y(j),
> cost is 0 if X(i) = Y(j))
> )
> {code}
> Result:
> D(M,N) is the edit distance value.
> Example:
> Early Termination condition:
> So, for the given threshold T, we can stop the computation early if the values of three cases are greater than T. That is,
> min (D(i-1,j), D(i,j-1), D(i-1,j-1)) > T
> This holds since if the cost of all possible cases (insertion, deletion, and substitution) is greater than T, all future operations will be greater than T in any cases.
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