c# - How to reduce the execution time in Parallel.ForEach function? -

code:

parallel.foreach(     infomap,     map =>     {         var workitem = map.workitem;         var parentinviews = viewmaps;         var workbenchitem = map.workbenchitem;         string linktype = string.empty;          workitemlinkcollection linkedworkitems = workitem.workitemlinkhistory;         if (linkedworkitems != null && linkedworkitems.count > 0)             linktype = linkedworkitems[0].linktypeend.linktype.referencename;         else if (workitem != null)             linktype = workitem.store.workitemlinktypes.linktypeends["parent"].linktype.referencename;          if (!string.isnullorempty(linktype))         {             var viewmap = parentinviews.firstordefault();             if (viewmap != null)             {                 var linkname =  linktype;                 var childtype = viewmap.childtype;                  ilinkitem itm = factory.buildlinkitem(linkname, workbenchitem, workbenchitem);                 lock (addparents)                 {                     addparents.add(itm);                 }             }         }     }); 

factory.buildlinkitem definition:

public static ilinkitem buildlinkitem(string linkname, iworkbenchitem parent, iworkbenchitem child) {                 return new linkitem { linkname = linkname ?? string.empty, child = child, parent = parent }; } 

totally 658 items present , takes 10 seconds execute above parallel.foreach function.

is possible reduce execution time , if so, please suggest me solution. thanks.

note: apart parallel.foreach, if alternate method there increase performance , reduce execution time also, please suggest. thanks.

your problem in lock statement. mutex mechanism behind extremely performance expensive compared other synchronization mechanisms. i'm gonna bet 99.99% of 10 seconds, code spends locking , waiting in critical section. non-parallel select faster.

your have 2 options. first use .asparallel() .select() , .where() instead of parallel.foreach , adding collection inside lock. highly recommend this. way, synchronization between operation on different items handled automatically.

second option use kind of concurrent collection exist in .net 4 instead of locking , normal collection. collections specially optimized quick adding of items, threadsafe.

this little hack, how convert asparallel:

infomap.asparallel().select( map => {     var workitem = map.workitem;     var parentinviews = viewmaps;     var workbenchitem = map.workbenchitem;     string linktype = string.empty;      workitemlinkcollection linkedworkitems = workitem.workitemlinkhistory;     if (linkedworkitems != null && linkedworkitems.count > 0)         linktype = linkedworkitems[0].linktypeend.linktype.referencename;     else if (workitem != null)         linktype = workitem.store.workitemlinktypes.linktypeends["parent"].linktype.referencename;      if (!string.isnullorempty(linktype))     {         var viewmap = parentinviews.firstordefault();         if (viewmap != null)         {             var linkname =  linktype;             var childtype = viewmap.childtype;              ilinkitem itm = factory.buildlinkitem(linkname, workbenchitem, workbenchitem);              return new {item = itm, filter=true};         }     }     return new {item = (ilinkitem)null, filter=false}; }) .where(x=>x.filter) .select(x=>x.item) .tolist();