我可以使用MPI_Bcast進行同步嗎？

Question

我需要執行只能由主進程執行的操作。奴隸們什麼都不能做，只能等着主人完成。所以我做了以下（僞代碼，我將多數程序，所以我想有一個很難拿出實際MPI代碼。我希望評論是在解釋我在做什麼很清楚）

def routine(): 

    if not isMaster(): 
     # I am a slave. I just sit here, waiting for the master to finish. 
     # wait for a string from the master explaining the state 
     string = MPI_Bcast("whatever", 0) 
     return (string == "SUCCESS") 

    <master does its long running business> 

    string = MPI_Bcast("SUCCESS", 0) # tell the slaves it worked fine. 

    return True 

不這項工作，還是我濫用廣播？

Answer 1

如果你作出這樣的僞代碼：

def routine(): 

    if not isMaster(): 
     # I am a slave. I just sit here, waiting for the master to finish. 
     # wait for a string from the master explaining the state 
     string = MPI_Bcast("whatever", 0) 
     return (string == "SUCCESS") 

    else: 
     <master does its long running business> 
     string = MPI_Bcast("SUCCESS", 0) # tell the slaves it worked fine. 

    return True 

那麼你應該罰款。 （當然，您需要確保爲您的語言正確獲取特定的MPI API。）通常，對於廣播或任何集體操作，通信器中的每個等級都需要執行相同數量的呼叫。爲了理解，以相同源代碼行上的每個等級無條件執行Bcast的方式重構程序可能是有益的，例如，

def routine(): 
    status_code = UNKNOWN 
    if isMaster(): 
     #do stuff 
     status_code = OK 

    MPI_Bcast(&status_code, 0) 
    #check status_code on each rank