http://www.csie.ntu.edu.tw/~cjlin/libsvmtools/datasets/binary.html#news20.binary
head -1000 news20.binary | sed 's/+1/1/g' | sed 's/-1/0/g' > news20.binary.1000
sort -R news20.binary > news20.random
head -1000 news20.random | sed 's/+1/1/g' | sed 's/-1/0/g' > news20.random.1000