[GitHub] jixuan1989 opened a new pull request #83: [IOTDB-31] Set the float precision of data in memtable

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jixuan1989 opened a new pull request #83: [IOTDB-31] Set the float precision of data in memtable
URL: https://github.com/apache/incubator-iotdb/pull/83
 
 
   Now the program logic is:
   * When writing data into the memory, we do not control the precision, so that we can get the best ingestion performance.
   * When querying data from disk, we do not need additional operations, because when data is flushing on disk, it will be processed to only remain the required precision.
   * When querying data from memory which is not flushed on disk, we process this part of data to control its precision.
   
   I use `Math.round()` method to implement the precision control, which only takes  less than 1/10 additional time cost. (performance test codes: see comments in JIRA 31)
   
   As the limitation of Java's `Math.round(float)` and `Math.round(double)`,  the value range of float/double is constrained:
   
   * For Float data value, The data range is (-Integer.MAX_VALUE, Integer.MAX_VALUE), rather than Float.MAX_VALUE, and the max_point_number is 19.
   * For Double data value, The data range is (-Long.MAX_VALUE, Long.MAX_VALUE), rather than Double.MAX_VALUE, and the max_point_number is 19.
   
   
   

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