用stata的64核版本，可以快很多的，论坛里面有

compress命令

楼上已经给出了答案。
Title

[D] compress -- Compress data in memory


Syntax

compress [varlist]


Menu

Data > Data utilities > Optimize variable storage


Description

compress attempts to reduce the amount of memory used by your data.


Remarks

compress reduces the size of your dataset by considering demoting

doubles   to   longs, ints, or bytes
floats    to   ints or bytes
longs     to   ints or bytes
ints      to   bytes
strings   to   shorter strings

See [D] data types for an explanation of these storage types.

compress leaves your data logically unchanged but (probably) appreciably smaller.        compress
never makes a mistake, results in loss of precision, or hacks off strings.