Problem 861. Memory Map File: Access and Update

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>Challenge is to read data from a memory map file and also update the file.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Memory Mapping allows placing large static arrays in virtual memory with good point access times. Minimal consumption of valuable RAM occurs. Medium size TB files can be Mapped on a 64 bit machine. Who has TBs of Hard drive?</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>With Write Access the Actual file gets data permanently overwritten.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>(Note: 8GB logical vector took 60 sec on first large access. Subsequent large accesses returned in msec domain)</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Applications include</w:t></w:r><w:r><w:t> </w:t></w:r><w:hyperlink w:docLocation=\"http://www.mathworks.com/products/demos/bioinfo/biomemorymapdemo/biomemorymapdemo.html\"><w:r><w:t>Genome Mapping</w:t></w:r></w:hyperlink><w:r><w:t> .</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> Memory Mapped Variable</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> Value of location 1</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Update location 2 to value of 2</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>Example:</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>x is variable</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"code\"/></w:pPr><w:r><w:t><![CDATA[x.data(1:4) is [1234 1111 54543 32465]\nChange x.data(2) to 2 \nx.data(1:4) becomes [1234 2 54543 32465]\nOutput location 1 value: 1234]]></w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Follow Up Challenge: Busting the Cody 3GB Memory Limit using multiple mapped files.</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>"}]}

Challenge is to read data from a memory map file and also update the file.Memory Mapping allows placing large static arrays in virtual memory with good point access times. Minimal consumption of valuable RAM occurs. Medium size TB files can be Mapped on a 64 bit machine. Who has TBs of Hard drive?With Write Access the Actual file gets data permanently overwritten.(Note: 8GB logical vector took 60 sec on first large access. Subsequent large accesses returned in msec domain)Applications include <a href="http://www.mathworks.com/products/demos/bioinfo/biomemorymapdemo/biomemorymapdemo.html">Genome Mapping</a> .Input: Memory Mapped VariableOutput: 
Value of location 1Update location 2 to value of 2Example:x is variable<pre class="language-matlab">x.data(1:4) is [1234 1111 54543 32465]
Change x.data(2) to 2 
x.data(1:4) becomes [1234 2 54543 32465]
Output location 1 value: 1234
</pre>Follow Up Challenge: Busting the Cody 3GB Memory Limit using multiple mapped files.

Solve

Solution Stats

22 Solutions
13 Solvers

Last Solution submitted on Jul 04, 2022

Last 200 Solutions

Problem Comments

1 Comment

1 Comment

Rafael S.T. Vieira on 31 Oct 2020

I am not sure that I understand the goal of this problem. Memory mapping does not decrease size. Only compression can do it as far as I know (and as long as we are using the adequate data type to our data).

Problem Recent Solvers13

Problem Tags

Community Treasure Hunt

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

Start Hunting!

Problem 861. Memory Map File: Access and Update

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers13

Suggested Problems

More from this Author260

Problem Tags

Community Treasure Hunt

Problem 861. Memory Map File: Access and Update

Solution Stats

Last 200 Solutions

Problem Comments

Problem Recent Solvers13

Suggested Problems

More from this Author260

Problem Tags

Community Treasure Hunt

Players