pyabc: allow returning large result from sub processes

src/python/pyabc.i

@@ -755,6 +755,16 @@ def _retry_read(fd):
                 continue
             raise
 
+def _retry_os_read(fd):
+
+    while True:
+        try:
+            return os.read(fd, 1)
+        except OSError as e:
+            if e.errno == errno.EINTR:
+                continue
+            raise
+
 def _retry_wait():
 
     while True:
@@ -817,6 +827,7 @@ def _child_wait_thread_func(fd):
                     _active_pids.remove(pid)
                     
                 _terminated_pids[pid] = status
+                os.write(_wait_fd_write, "1")
                 _terminated_pids_cond.notifyAll()
 
 _sigint_pipe_read_fd = -1
@@ -825,8 +836,14 @@ _sigint_pipe_write_fd = -1
 _sigchld_pipe_read_fd = -1
 _sigchld_pipe_write_fd = -1
 
+wait_fd = -1
+_wait_fd_write = -1
+
 def _start_threads():
 
+    global wait_fd, _wait_fd_write
+    wait_fd, _wait_fd_write = os.pipe()
+
     global _sigint_pipe_read_fd, _sigint_pipe_write_fd
     
     _sigint_pipe_read_fd, _sigint_pipe_write_fd = os.pipe()
@@ -865,6 +882,9 @@ def after_fork():
         
     _close_on_fork = []
 
+    os.close(wait_fd)
+    os.close(_wait_fd_write)
+
     os.close(_sigint_pipe_read_fd)
     os.close(_sigint_pipe_write_fd)
     
@@ -934,6 +954,7 @@ def _waitpid(pid, options=0):
         with _active_lock:
         
             if pid in _terminated_pids:
+                _retry_os_read(wait_fd)
                 status = _terminated_pids[pid]
                 del _terminated_pids[pid]
                 return pid, status
@@ -950,6 +971,7 @@ def _wait(options=0):
         with _active_lock:
         
             for pid, status in _terminated_pids.iteritems():
+                _retry_os_read(wait_fd)
                 del _terminated_pids[pid]
                 return pid, status
             

src/python/pyabc_split.py

@@ -82,20 +82,36 @@ Author: Baruch Sterin <sterin@berkeley.edu>
 """
 
 import os
+import select
+import fcntl
 import errno
 import sys
-import pickle
+import cPickle as pickle
 import signal
+import cStringIO
+
 from contextlib import contextmanager
 
 import pyabc
 
+def _retry_select(rlist):
+    while True:
+        try:
+            rrdy,_,_ = select.select(rlist,[],[])
+            if rrdy:
+                return rrdy
+        except select.error as e:
+            if e[0] == errno.EINTR:
+                continue
+            raise
+
 class _splitter(object):
     
     def __init__(self, funcs):
         self.funcs = funcs
         self.pids = []
         self.fds = {}
+        self.buffers = {}
         self.results = {}
     
     def is_done(self):
@@ -117,6 +133,7 @@ class _splitter(object):
             self.results[pid] = None
             
         self.fds = {}
+        self.buffers = {}
 
     def child( self, fdw, f):
         # call function
@@ -133,6 +150,9 @@ class _splitter(object):
         # create a pipe to communicate with the child process
         pr,pw = os.pipe()
         
+        # set pr to be non-blocking
+        fcntl.fcntl(pr, fcntl.F_SETFL, os.O_NONBLOCK)
+        
         parentpid = os.getpid()
         rc = 1
         
@@ -162,23 +182,53 @@ class _splitter(object):
             pid, fd = self.fork_one(f)
             self.pids.append(pid)
             self.fds[pid] = (i,fd)
+            self.buffers[fd] = cStringIO.StringIO()
+    
+    def communicate(self):
+        
+        rlist = [ fd for _, (_,fd) in self.fds.iteritems() ]
+        rlist.append(pyabc.wait_fd)
+
+        stop = False
+        
+        while not stop:
+
+            rrdy = _retry_select( rlist )
+            
+            for fd in rrdy:
+                
+                if fd == pyabc.wait_fd:
+                    stop = True
+                    continue
+                    
+                self.buffers[fd].write( os.read(fd, 16384) )
     
     def get_next_result(self):
 
+        # read from the pipes as needed, while waiting for the next child process to terminate
+        self.communicate()
+    
         # wait for the next child process to terminate
         pid, rc = os.wait()
         assert pid in self.fds
         
-        # retrieve the pipe file descriptor1
+        # retrieve the pipe file descriptor
         i, fd = self.fds[pid]
         del self.fds[pid]
 
-        assert pid not in self.fds
+        # retrieve the buffer
+        buffer = self.buffers[fd]
+        del self.buffers[fd]
+
+        # fill the buffer
+        while True:
+            s = os.read(fd, 16384)
+            if not s:
+                break
+            buffer.write(s)
 
-        # read result from file
-        with os.fdopen( fd, "r" ) as fin:
         try:
-                return (i,pickle.load(fin))
+            return (i, pickle.loads(buffer.getvalue()))
         except EOFError, pickle.UnpicklingError:
             return (i, None)