topic Re: Iterating data step in SAS Programming

Iterating data step

kaditor — Fri, 10 Jun 2016 04:33:18 GMT

Hi ,

I am trying to match controls to cases using gmatch macro(by Eric bregstralh). The processing time is fairly fast (3min) if I use 100 cases and 2000000 controls as the source data. However, I applied this macro to my unmatched case/control data [n=10832090 (cases =345013, pool of potential controls=10487077)] and its taking longer to process (four days now).

Here is the code I used to process the 100cases/2000000 potential controls. Is it want to iterate until the last case is matched to 4 possible controls?

%include "C:\SAS programs\gmatch.sas";

/**randomly selecting 100 cases without replacement**/

PROC SURVEYSELECT DATA=casecontrol( WHERE=(case = 1))
OUT=case
METHOD=SRS
N=100
SEED=1420;
ID uniqueid gender yob ethnicity1 ;
RUN;
QUIT;

/**randomly selecting 2000000 controls without replacement**/
PROC SURVEYSELECT DATA=casecontrol ( WHERE=(T2DMstatus =0))
OUT=control
METHOD=SRS
N=2000000
SEED=345;
ID uniqueid gender yob ethnicity1 ;
RUN;
QUIT;

proc sort data=case; by uniqueid;run;
proc sort data=control;by uniqueid;run;

data unmatched;
set case control;
by uniqueid;

run;

%gmatch(data=unmatched,group=t2dmstatus,id=uniqueid,mvars= gender yob ethnicity1,wts=10 1 4,dmaxk=0 1 0,
dist=1,transf =1, contls=4,seedca=67,seedco=99,out=greedymatched,outnmca=nonmathcedcases,outnmco=nonmathchedcontrols);

data match;
set greedymatched;
run;

/**creating a dataset that doesn't contain the matches just made from above**/

/** next random selection of cases and controls should be done on this dataset**/
PROC SQL;
CREATE TABLE potential_match AS
SELECT *
FROM casecontrol_2014
WHERE uniqueid NOT IN (SELECT __IDCA FROM match)
AND uniqueid NOT IN (SELECT __IDCO FROM match);

%END;

/***************************************************************************/

I want to be able to repeat this whole process until the dataset potential_match has no more case. This process is likely to produce close to 3000 datasets that will be merged.

Re: Iterating data step

Astounding — Fri, 10 Jun 2016 13:47:28 GMT

At a minimum, you will have to tell us a little more. Where is the program hanging up? Before the macro starts, in the middle of the macro, after the macro ends? Where can we find a copy of the macro? Does the log file keep getting larger or not?

Four days sounds like an unreasonable amount of time. It is possible that the larger sizes have used up some other resource such as the space in the WORK area, and that no further processing is able to take place.

Re: Iterating data step

ballardw — Fri, 10 Jun 2016 15:17:36 GMT

Without know the specific macro it is a bit difficult to discuss. BUT you have multiplied the case numbers by 3450, the controls by 5.2.

If the process time expands linearly that would mean an expected time approximately 3450*5.2*3 (minutes) => about 37.4 days by my estimate.

If the actuall code is doing anything approaching cartesian joins of stuff then the time may not increase linearly but more of an n-squared.