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

Created by Richard Zapor

Solve Later

{"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>"}]}

Solve

Solution Stats

24 Solutions
14 Solvers

Last Solution submitted on Dec 31, 2020

Last 200 Solutions

Problem Comments

6 Comments

6 Comments

Show 3 older comments

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.

Problem Recent Solvers14

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

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

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers14

Suggested Problems

More from this Author247

Problem Tags

Community Treasure Hunt

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

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers14

Suggested Problems

More from this Author247

Problem Tags

Community Treasure Hunt

Players