C4SChunk.java

package water.fvec;

import java.util.Arrays;
import water.*;

/**
 * The scale/bias function, where data is in SIGNED bytes before scaling.
 */
public class C4SChunk extends Chunk {
  static private final long _NA = Integer.MIN_VALUE;
  static final int OFF=8+8;
  public double _scale;
  long _bias;
  C4SChunk( byte[] bs, long bias, double scale ) { _mem=bs; _start = -1; _len = (_mem.length-OFF)>>2;
    _bias = bias; _scale = scale;
    UDP.set8d(_mem,0,scale);
    UDP.set8(_mem, 8, bias);
  }
  @Override protected final long at8_impl( int i ) {
    long res = UDP.get4(_mem,(i<<2)+OFF);
    if( res == _NA ) throw new IllegalArgumentException("at8 but value is missing");
    return (long)((res + _bias)*_scale);
  }
  @Override protected final double atd_impl( int i ) {
    long res = UDP.get4(_mem,(i<<2)+OFF);
    return (res == _NA)?Double.NaN:(res + _bias)*_scale;
  }
  @Override protected final boolean isNA_impl( int i ) { return UDP.get4(_mem,(i<<2)+OFF) == _NA; }
  @Override boolean set_impl(int idx, long l) {
    long res = (long)(l/_scale)-_bias; // Compressed value
    double d = (res+_bias)*_scale;     // Reverse it
    if( (long)d != l ) return false;   // Does not reverse cleanly?
    if( !(Integer.MIN_VALUE < res && res <= Integer.MAX_VALUE) ) return false; // Out-o-range for a int array
    UDP.set4(_mem,(idx<<2)+OFF,(int)res);
    return true;
  }
  @Override boolean set_impl(int i, double d) { return false; }
  @Override boolean set_impl(int i, float f ) { return false; }
  @Override boolean setNA_impl(int idx) { UDP.set4(_mem,(idx<<2)+OFF,(int)_NA); return true; }
  @Override boolean hasFloat() { return _scale < 1.0; }
  @Override public AutoBuffer write(AutoBuffer bb) { return bb.putA1(_mem,_mem.length); }
  @Override public C4SChunk read(AutoBuffer bb) {
    _mem = bb.bufClose();
    _start = -1;
    _len = (_mem.length-OFF)>>2;
    _scale= UDP.get8d(_mem,0);
    _bias = UDP.get8(_mem, 8);
    return this;
  }
  @Override NewChunk inflate_impl(NewChunk nc) {
    double dx = Math.log10(_scale);
    assert PrettyPrint.fitsIntoInt(dx);
    nc.set_len(nc.set_sparseLen(0));
    final int len = len();
    for( int i=0; i<len; i++ ) {
      int res = UDP.get4(_mem,(i<<2)+OFF);
      if( res == _NA ) nc.addNA();
      else nc.addNum(res+_bias,(int)dx);
    }
    return nc;
  }
  public int pformat_len0() { return pformat_len0(_scale,5); }
  public String pformat0() { return "% 10.4e"; }
}