Problem 861. Memory Map File: Access and Update

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>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.

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Problem 861. Memory Map File: Access and Update

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