How to copy pointgroup from different time

[Arthur~Chiu]

i want to copy pointgroup at one frame ,and to use this pointgroup at different time，but when i use it at other time ,it will error, 

 

/////code

gdp = (GU_Detail *)sop->getCookedGeo(context);

 

GA_PointGroup *point_group =0;

if(!point_group)

    point_group  = gdp->newPointGroup("_ss_",1);

point_group->clear();

 

//append point offset in the group

for（）  

{

   point_group->addOffset(i)；

}

 

//now i have a pointgroup

 

//time set code

context.setTime(OPgetDirector()->getChannelManager()->getTime(*(user_time)));

gdp = (GU_Detail *)sop->getCookedGeo(context);

 

cout<<point_group->entris();

error 

 

the "user_time" is variable 

 

why ?and how to fix ? someone can help me? thanks!