pyabc_split.py

"""
module pyabc_split

Executes python functions and their arguements as separate processes and returns their return values through pickling. This modules offers a single function:

Function: split_all(funcs)

The function returns a generator objects that allowes iteration over the results,

Arguments:

funcs: a list of tuples (f, args) where f is a python function and args is a collection of arguments for f.

Caveats:

1. Global variables in the parent process are not affected by the child processes.
2. The functions can only return simple types, see the pickle module for details

Usage:

Assume you would like to run the function f_1(1), f_2(1,2), f_3(1,2,3) in different processes. 

def f_1(i):
    return i+1
    
def f_2(i,j):
    return i*10+j+1
    
def f_3(i,j,k):
    return i*100+j*10+k+1

Construct a tuple of the function and arguments for each function

t_1 = (f_1, [1])
t_2 = (f_2, [1,2])
t_3 = (f_3, [1,2,3])

Create a list containing these tuples:

funcs = [t_1, t_2, t_3]

Use the function split_all() to run these functions in separate processes:

for res in split_all(funcs):
    print res
    
The output will be:

2
13
124

(The order may be different, except that in this case the processes are so fast that they terminate before the next one is created)

Alternatively, you may quite in the middle, say after the first process returns:

for res in split_all(funcs):
    print res
    break
    
This will kill all processes not yet finished.

To run ABC operations, that required saving the child process state and restoring it at the parent, use abc_split_all().

    import pyabc
    
    def abc_f(truth):
        import os
        print "pid=%d, abc_f(%s)"%(os.getpid(), truth)
        pyabc.run_command('read_truth %s'%truth)
        pyabc.run_command('strash')
        
    funcs = [
        defer(abc_f)("1000"),
        defer(abc_f)("0001")
    ]
    
    for _ in abc_split_all(funcs):
        pyabc.run_command('write_verilog /dev/stdout')

Author: Baruch Sterin <sterin@berkeley.edu>
"""

import os
import errno
import sys
import pickle
import signal
from contextlib import contextmanager

import pyabc

class _splitter(object):
    
    def __init__(self, funcs):
        self.funcs = funcs
        self.pids = []
        self.fds = {}
        self.results = {}
    
    def is_done(self):
        return len(self.fds) == 0
    
    def cleanup(self):
        # close pipes and kill child processes
        for pid,(i,fd) in self.fds.iteritems():
            os.close(fd)
            try:
                os.kill( pid, signal.SIGINT )
            except Exception as e:
                print >>sys.stderr, 'exception while trying to kill pid=%d: '%pid, e
                raise
        
            # wait for termination and update result
        for pid, _ in self.fds.iteritems():
            os.waitpid( pid, 0 )
            self.results[pid] = None
            
        self.fds = {}

    def child( self, fdw, f):
        # call function
        res = f()
        
        # write return value into pipe
        with os.fdopen( fdw, "w" ) as fout:
            pickle.dump(res, fout)
            
        return 0

    def fork_one(self, f):
        
        # create a pipe to communicate with the child process
        pr,pw = os.pipe()
        
        parentpid = os.getpid()
        rc = 1
        
        try:

            # create child process
            pid = os.fork()
    
            if pid == 0:
                # child process:
                os.close(pr)
                pyabc.close_on_fork(pw)
                
                rc = self.child( pw, f)
                os._exit(rc)
            else:
                # parent process:
                os.close(pw)
                return (pid, pr)
                
        finally:
            if os.getpid() != parentpid:
                os._exit(rc)

    def fork_all(self):
        for i,f in enumerate(self.funcs):
            pid, fd = self.fork_one(f)
            self.pids.append(pid)
            self.fds[pid] = (i,fd)
    
    def get_next_result(self):
    
        # wait for the next child process to terminate
        pid, rc = os.wait()
        assert pid in self.fds
        
        # retrieve the pipe file descriptor1
        i, fd = self.fds[pid]
        del self.fds[pid]
        
        assert pid not in self.fds
        
        # read result from file
        with os.fdopen( fd, "r" ) as fin:
            try:
                return (i,pickle.load(fin))
            except EOFError, pickle.UnpicklingError:
                return (i, None)

@contextmanager
def _splitter_wrapper(funcs):
    # ensure cleanup of child processes
    s = _splitter(funcs)
    try:
        yield s
    finally:
        s.cleanup()

def split_all_full(funcs):
    # provide an iterator for child process result
    with _splitter_wrapper(funcs) as s:
        
        s.fork_all()
        
        while not s.is_done():
            yield s.get_next_result()

def defer(f):
    return lambda *args, **kwargs: lambda : f(*args,**kwargs)

def split_all(funcs):
    for _, res in split_all_full( ( defer(f)(*args) for f,args in funcs ) ):
        yield res

import tempfile

@contextmanager
def temp_file_names(suffixes):
    names = []
    try:
        for suffix in suffixes:
            with tempfile.NamedTemporaryFile(delete=False, suffix=suffix) as file:
                names.append( file.name )
        yield names
    finally:
        for name in names:
            os.unlink(name)

class abc_state(object):
    def __init__(self):
        with tempfile.NamedTemporaryFile(delete=False, suffix='.aig') as file:
            self.aig = file.name
        with tempfile.NamedTemporaryFile(delete=False, suffix='.log') as file:
            self.log = file.name
        pyabc.run_command(r'write_status %s'%self.log)
        pyabc.run_command(r'write_aiger %s'%self.aig)
    
    def __del__(self):
        os.unlink( self.aig )
        os.unlink( self.log )

    def restore(self):
        pyabc.run_command(r'read_aiger %s'%self.aig)
        pyabc.run_command(r'read_status %s'%self.log)

def abc_split_all(funcs):
    import pyabc
    
    def child(f, aig, log):
        res = f()
        pyabc.run_command(r'write_status %s'%log)
        pyabc.run_command(r'write_aiger %s'%aig)
        return res
        
    def parent(res, aig, log):
        pyabc.run_command(r'read_aiger %s'%aig)
        pyabc.run_command(r'read_status %s'%log)
        return res
        
    with temp_file_names( ['.aig','.log']*len(funcs) ) as tmp:

        funcs = [ defer(child)(f, tmp[2*i],tmp[2*i+1]) for i,f in enumerate(funcs) ]
        
        for i, res in split_all_full(funcs):
            yield i, parent(res, tmp[2*i],tmp[2*i+1])

if __name__ == "__main__":
    
    # define some functions to run
    
    def f_1(i):
        return i+1
        
    def f_2(i,j):
        return i*10+j+1
        
    def f_3(i,j,k):
        return i*100+j*10+k+1
    
    # Construct a tuple of the function and arguments for each function
    
    t_1 = (f_1, [1])
    t_2 = (f_2, [1,2])
    t_3 = (f_3, [1,2,3])

    # Create a list containing these tuples:

    funcs = [t_1, t_2, t_3]

    # Use the function split_all() to run these functions in separate processes:

    for res in split_all(funcs):
        print res

    # Alternatively, quit after the first process returns:
    
    for res in split_all(funcs):
        print res
        break
        
    # For operations with ABC that save and restore status
    
    import pyabc
    
    def abc_f(truth):
        import os
        print "pid=%d, abc_f(%s)"%(os.getpid(), truth)
        pyabc.run_command('read_truth %s'%truth)
        pyabc.run_command('strash')
        return 100
        
    funcs = [
        defer(abc_f)("1000"),
        defer(abc_f)("0001")
    ]
    
    best = None
    
    for i, res in abc_split_all(funcs):
        print i, res
        if best is None:\
            # save state
            best = abc_state()
        pyabc.run_command('write_verilog /dev/stdout')
    
    # if there is a saved state, restore it
    if best is not None:
        best.restore()
        pyabc.run_command('write_verilog /dev/stdout')