psage.py

r"""
Parallel Interface to the Sage interpreter

This is an expect interface to \emph{multiple} copy of the \sage
interpreter, which can all run simultaneous calculations.  A PSage
object does not work as well as the usual Sage object, but does have
the great property that when you construct an object in a PSage you
get back a prompt immediately.  All objects constructed for that
PSage print <<currently executing code>> until code execution
completes, when they print as normal.

\note{BUG -- currently non-idle PSage subprocesses do not stop when
\sage exits.  I would very much like to fix this but don't know how.}

EXAMPLES:

We illustrate how to factor 3 integers in parallel.
First start up 3 parallel Sage interfaces::

    sage: v = [PSage() for _ in range(3)]

Next, request factorization of one random integer in each copy. ::

    sage: w = [x('factor(2^%s-1)'% randint(250,310)) for x in v]  # long time (5s on sage.math, 2011)

Print the status::

    sage: w       # long time, random output (depends on timing)
    [3 * 11 * 31^2 * 311 * 11161 * 11471 * 73471 * 715827883 * 2147483647 * 4649919401 * 18158209813151 * 5947603221397891 * 29126056043168521,
     <<currently executing code>>,
     9623 * 68492481833 * 23579543011798993222850893929565870383844167873851502677311057483194673]

Note that at the point when we printed two of the factorizations had
finished but a third one hadn't.   A few seconds later all three have
finished::

    sage: w       # long time, random output
    [3 * 11 * 31^2 * 311 * 11161 * 11471 * 73471 * 715827883 * 2147483647 * 4649919401 * 18158209813151 * 5947603221397891 * 29126056043168521,
     23^2 * 47 * 89 * 178481 * 4103188409 * 199957736328435366769577 * 44667711762797798403039426178361,
     9623 * 68492481833 * 23579543011798993222850893929565870383844167873851502677311057483194673]
"""

import os, time

from sage0 import Sage, SageElement


number = 0


class PSage(Sage):
    def __init__(self,  **kwds):
        if kwds.has_key('server'):
            raise NotImplementedError, "PSage doesn't work on remote server yet."
        Sage.__init__(self, **kwds)
        import sage.misc.misc
        T = sage.misc.misc.tmp_dir('sage_smp')
        self.__tmp_dir = T
        self.__tmp = '%s/lock'%T
        self._unlock()
        self._unlock_code = "open('%s','w').write('__unlocked__')"%self.__tmp

        global number
        self._number = number
        number += 1

    def __repr__(self):
        return 'A running non-blocking (parallel) instance of Sage (number %s)'%(self._number)

    def _unlock(self):
        self._locked = False
        open(self.__tmp, 'w').write('__unlocked__')

    def _lock(self):
        self._locked = True
        open(self.__tmp, 'w').write('__locked__')

    def _start(self):
        Sage._start(self)
        self.expect().timeout = 0.25
        self.expect().delaybeforesend = 0.01

    def is_locked(self):
        if open(self.__tmp).read() == '__locked__':
            try:
                self.expect().expect(self._prompt)
                self.expect().expect(self._prompt)
            except:
                pass
        return open(self.__tmp).read() == '__locked__'

    def __del__(self):
        print "deleting"
        for x in os.listdir(self.__tmp_dir):
            os.remove('%s/%s'%(self.__tmp_dir, x))
        os.removedirs(self.__tmp_dir)
        if not (self._expect is None):
            cmd = 'kill -9 %s'%self._expect.pid
            print cmd
            os.system(cmd)
        Sage.__del__(self)
        
    def eval(self, x, strip=True, **kwds):
        """
            x -- code
            strip --ignored
        """
        if self.is_locked():
            return "<<currently executing code>>"
        if self._locked:
            self._locked = False
            #self._expect.expect('__unlocked__')
            self.expect().send('\n')
            self.expect().expect(self._prompt)
            self.expect().expect(self._prompt)
        try:
            return Sage.eval(self, x, **kwds)
        except:
            return "<<currently executing code>>"
            

    def get(self, var):
        """
        Get the value of the variable var.
        """
        try:
            return self.eval('print %s'%var)
        except:
            return "<<currently executing code>>"

    def set(self, var, value):
        """
        Set the variable var to the given value.
        """
        cmd = '%s=%s'%(var,value)        
        self._send_nowait(cmd)
        time.sleep(0.02)

    def _send_nowait(self, x):
        if x.find('\n') != -1:
            raise ValueError, "x must not have any newlines"
        # Now we want the client Python process to execute two things.
        # The first is x and the second is c.  The effect of c
        # will be to unlock the lock.
        if self.is_locked():
            return "<<currently executing code>>"
        E = self.expect()
        self._lock()
        E.write(self.preparse(x) + '\n')
        try:
            E.expect(self._prompt)
        except:
            pass
        E.write(self._unlock_code + '\n\n')

    def _object_class(self):
        return PSageElement
        
class PSageElement(SageElement):
    def is_locked(self):
        return self.parent().is_locked()