Sorting in GAMS

This question came up during a workshop I taught at a large power company:

I want to generate a number of load-duration and price-duration curves, but it takes too long.

Here is a small example demonstrating some formulations for sorting a 1d parameter:

option profile=1; set i /i1*i10000/; parameter p(i); p(i) = uniform(1,100); display p; execute_unload "p",p; execute "gdxrank p.gdx p2.gdx"; parameter pindex(i); execute_load "p2.gdx",pindex=p; display pindex; * slow parameter p2(i); alias(i,j); p2(i)=sum(j$(ord(i)=pindex(j)),p(j)); display p2; * almost as slow parameter p3(i); alias(i,j); loop((i,j)$(ord(i)=pindex(j)),    p3(i)=p(j); ); display p3; * fast using trick: parameter p4(i); p4(i+(pindex(i)-ord(i))) = p(i); display p4;

The timings are:

Method	Time (seconds)
SUM (assignment to p2)	28.407
LOOP (assignment to p3)	22.230
TRICK (assignment to p4)	0.265