Problem 955. ismember: Enhanced Time Performance for 'rows' - Speed Scoring (90% savings)

Created by Richard Zapor

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{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>The Challenge is to perform very fast the 'ismember' function for a long and wide array.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>The data is small integer representing data permutations of items like DNA and Rubik's cube faces and orientations.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:b/></w:rPr><w:t>Input:</w:t></w:r><w:r><w:t> Array of uint8 of dimensions (m, 16) with values 0:3</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:b/></w:rPr><w:t>Output:</w:t></w:r><w:r><w:t> Array Equivalent to ismember(A,B,'rows')</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:rPr><w:b/></w:rPr><w:t>Hints:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>1) Columns can be merged to form a reduced number of columns 2) Unique has the option to provide an Array and a sorting Index</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

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24 Solutions
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Last Solution submitted on Dec 31, 2020

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Jean-Marie Sainthillier on 1 Oct 2013

I try but I don't understand the merge function (Alfonso and Richard solutions). Can you explain ?

Alfonso Nieto-Castanon on 1 Oct 2013

since numbers only range from 0 to 3 you may consider each row of A or B as a 16-digit base-4 number and just convert it to a 32-bit integer...

Jean-Marie Sainthillier on 1 Oct 2013

Ok. Thanks.

Jean-Marie Sainthillier on 1 Oct 2013

But if we have less restrictions on the input range (for example values between 0 and 255) ?

Richard Zapor on 3 Oct 2013

Jean-Marie, the methodology of converting multiple column value words into a single value has limited but specific applications where value ranges are limited. In the case of DNA sequencing the values can be made numeric 0:3. For ranges up to 255 the width gets limited to stay under the 2^64, or 2^53 limit for double. This challenge was a demonstration of a method to improve performance for functions like ismember.

Jean-Marie Sainthillier on 3 Oct 2013

Thank you.

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Problem 955. ismember: Enhanced Time Performance for 'rows' - Speed Scoring (90% savings)

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Problem 955. ismember: Enhanced Time Performance for 'rows' - Speed Scoring (90% savings)

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