问题 尚未支持mclapply长向量

我正在尝试运行一些R代码，因为内存而崩溃了。我得到的错误是：

Error in sendMaster(try(lapply(X = S, FUN = FUN, ...), silent = TRUE)) : 
  long vectors not supported yet: memory.c:3100

产生麻烦的功能如下：

StationUserX <- function(userNDX){
  lat1 = deg2rad(geolocation$latitude[userNDX])
  long1 = deg2rad(geolocation$longitude[userNDX])
  session_user_id = as.character(geolocation$session_user_id[userNDX])
  #Find closest station
  Distance2Stations <- unlist(lapply(stationNDXs, Distance2StationX, lat1, long1))
  # Return index for closest station and distance to closest station
  stations_userX = data.frame(session_user_id = session_user_id, 
                              station = ghcndstations$ID[stationNDXs], 
                              Distance2Station = Distance2Stations)    
  stations_userX = stations_userX[with(stations_userX, order(Distance2Station)), ]
  stations_userX = stations_userX[1:100,] #only the 100 closest stations...
  row.names(stations_userX)<-NULL
  return(stations_userX)
}

我用mclapply运行这个函数50k次。 StationUserX呼叫Distance2StationX 90k次。

是否有明显的方法来优化StationUserX功能？