Fei Hu created SYSTEMML-1831:
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Summary: Improve the efficiency of matrix subsetting
Key: SYSTEMML-1831
URL: https://issues.apache.org/jira/browse/SYSTEMML-1831
Project: SystemML
Issue Type: Improvement
Reporter: Fei Hu
For the {{rangeReIndex}} operation, it needs to read the whole input matrix
into memory first and do the subsetting in the memory. It is not efficient
because it needs to read a lot of unnecessary data, and even out of memory if
the size of input matrix exceeds the available memory.
The plan here is to read the keys in the Hadoop sequence file, and identify the
keys overlapped with the input range index. Then the values specified by the
identified keys will be read.
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