I am learning to write PROC DS2, some materials says there is a threads= option, which enables SAS use multiple threads to run program, so SAS can run faster. I write the following program:
data test1;
set sashelp.class;
do i=1 to 3e6;
output;
end;
run;
*Normal data step;
data test2;
set test1;
sum_age+age;
run;
proc delete data=test2;
run;
*Data step in DS2, without multiple threads;
proc ds2;
data test3/overwrite=yes;
method run();
dcl int sum_age;
set test1;
sum_age+age;
end;
enddata;
run;
quit;
proc delete data=test3;
run;
*Data step in DS2, with multiple threads;
proc ds2;
thread t/overwrite=yes;
method run();
dcl int sum_age;
set test1;
sum_age+age;
end;
endthread;
run;
data test4/overwrite=yes;
dcl thread t t_instance;
method run();
set from t_instance threads=8;
end;
enddata;
run;
quit;
Well, I just can't understand the running time:
Normal data step
real time: 2.97 seconds
cpu time: 2.87 seconds
Data step in DS2, without multiple threads
real time: 6.83 seconds
cpu time: 8.06 seconds
Data step in DS2, with multiple threads
real time: 4.47 seconds
cpu time: 13.26 seconds
And I write proc delete before taking each test, to keep the WORK library clean. My questions are:
1. Why data step in ds2 without multiple threads costs much time than normal data step?
2. Why data step in ds2 with multiple threads costs much time than normal data step? Even I let threads=16, there is not significant difference on real time.
