checkin broadcast python module

Makefile

@@ -47,4 +47,5 @@ $(SLIB) :
 	$(CXX) $(CFLAGS) -shared -o $@ $(filter %.cpp %.o %.c %.cc %.a, $^)
 
 clean:
-	$(RM) $(OBJ) $(MPIOBJ) $(ALIB) $(MPIALIB) *~ src/*~ include/*~ include/*/*~
+	$(RM) $(OBJ) $(MPIOBJ) $(ALIB) $(MPIALIB) *~ src/*~ include/*~ include/*/*~ wrapper/*~
+

wrapper/rabit.py

@@ -0,0 +1,126 @@
+"""
+Python interface for rabit
+  Reliable Allreduce and Broadcast Library
+Author: Tianqi Chen
+"""
+import cPickle as pickle
+import ctypes
+import os
+import sys
+if os.name == 'nt':
+    assert False, "Rabit windows is not yet compiled"
+else:
+    RABIT_PATH = os.path.dirname(__file__)+'/librabit_wrapper.so'
+
+# load in xgboost library
+rbtlib = ctypes.cdll.LoadLibrary(RABIT_PATH)
+rbtlib.RabitGetRank.restype = ctypes.c_int
+rbtlib.RabitGetWorldSize.restype = ctypes.c_int
+
+def check_err__():    
+    """
+    reserved function used to check error    
+    """
+    return
+
+def init(args = sys.argv):
+    """
+    intialize the rabit module, call this once before using anything
+    Arguments:
+        args: list(string)
+              the list of arguments used to initialized the rabit
+              usually you need to pass in sys.argv
+    """
+    arr = (ctypes.c_char_p * len(args))()
+    arr[:] = args
+    rbtlib.RabitInit(len(args), arr)
+    check_err__()
+
+def finalize():
+    """
+    finalize the rabit engine, call this function after you finished all jobs 
+    """
+    rbtlib.RabitFinalize()
+    check_err__()
+
+def get_rank():
+    """
+    Returns rank of current process
+    """
+    ret = rbtlib.RabitGetRank()
+    check_err__()
+    return ret
+
+def get_world_size():
+    """
+    Returns get total number of process
+    """
+    ret = rbtlib.RabitGetWorlSize()
+    check_err__()
+    return ret
+
+def tracker_print(msg):
+    """
+    print message to the tracker
+    this function can be used to communicate the information of the progress
+    to the tracker
+    """
+    if not isinstance(msg, str):
+        msg = str(msg)
+    rbtlib.RabitTrackerPrint(ctypes.c_char_p(msg).encode('utf-8'))
+    check_err__()
+
+def get_processor_name():
+    """
+    Returns the name of processor(host)
+    """
+    mxlen = 256
+    length = ctypes.c_ulong()
+    buf = ctypes.create_string_buffer(mxlen)
+    rbtlib.RabitGetProcessorName(buf, ctypes.byref(length),
+                                 mxlen)
+    check_err__()
+    return buf.value
+
+def broadcast(data, root):
+    """
+    broadcast object from one node to all other nodes
+    this function will return the broadcasted object
+
+    Example: the following example broadcast hello from rank 0 to all other nodes
+    ```python
+    import rabit
+    rabit.init()
+    if rabit.get_rank() == 0:
+        res = rabit.broadcast('hello', 0)
+    else:
+        res = rabit.broadcast(None, 0)
+    rabit.finalize()
+    ```
+    
+    Arguments:
+        data: anytype that can be pickled
+              input data, if current rank does not equal root, this can be None        
+        root: int
+              rank of the node to broadcast data from
+    """
+    rank = get_rank()
+    length = ctypes.c_ulong()
+    if root == rank:
+        assert data is not None, 'need to pass in data when broadcasting'
+        s = pickle.dumps(data, protocol = pickle.HIGHEST_PROTOCOL)
+        length.value = len(s)
+        dptr = (ctypes.c_char * length.value)()
+        dptr[:] = s
+    # run first broadcast
+    rbtlib.RabitBroadcast(ctypes.byref(length),
+                          ctypes.sizeof(ctypes.c_ulong),
+                          root)    
+    check_err__()
+    if root != rank:
+        dptr = (ctypes.c_char * length.value)()
+    # run second
+    rbtlib.RabitBroadcast(ctypes.cast(dptr, ctypes.c_void_p),
+                          length.value, root)
+    check_err__()
+    return  pickle.loads(dptr.value)