Merge pull request #1396 from MITx/feature/victor/randomization

Feature/victor/randomization

common/lib/xmodule/setup.py

@@ -29,6 +29,7 @@ setup(
             "error = xmodule.error_module:ErrorDescriptor",
             "problem = xmodule.capa_module:CapaDescriptor",
             "problemset = xmodule.seq_module:SequenceDescriptor",
+            "randomize = xmodule.randomize_module:RandomizeDescriptor", 
             "section = xmodule.backcompat_module:SemanticSectionDescriptor",
             "sequential = xmodule.seq_module:SequenceDescriptor",
             "slides = xmodule.backcompat_module:TranslateCustomTagDescriptor",

common/lib/xmodule/xmodule/capa_module.py

@@ -2,6 +2,7 @@ import cgi
 import datetime
 import dateutil
 import dateutil.parser
+import hashlib
 import json
 import logging
 import traceback
@@ -25,6 +26,22 @@ log = logging.getLogger("mitx.courseware")
 #-----------------------------------------------------------------------------
 TIMEDELTA_REGEX = re.compile(r'^((?P<days>\d+?) day(?:s?))?(\s)?((?P<hours>\d+?) hour(?:s?))?(\s)?((?P<minutes>\d+?) minute(?:s)?)?(\s)?((?P<seconds>\d+?) second(?:s)?)?$')
 
+# Generated this many different variants of problems with rerandomize=per_student
+NUM_RANDOMIZATION_BINS = 20
+
+def randomization_bin(seed, problem_id):
+    """
+    Pick a randomization bin for the problem given the user's seed and a problem id.
+
+    We do this because we only want e.g. 20 randomizations of a problem to make analytics
+    interesting.  To avoid having sets of students that always get the same problems,
+    we'll combine the system's per-student seed with the problem id in picking the bin.
+    """
+    h = hashlib.sha1()
+    h.update(str(seed))
+    h.update(str(problem_id))
+    # get the first few digits of the hash, convert to an int, then mod.
+    return int(h.hexdigest()[:7], 16) % NUM_RANDOMIZATION_BINS
 
 def only_one(lst, default="", process=lambda x: x):
     """
@@ -138,13 +155,9 @@ class CapaModule(XModule):
 
         if self.rerandomize == 'never':
             self.seed = 1
-        elif self.rerandomize == "per_student" and hasattr(self.system, 'id'):
-            # TODO: This line is badly broken:
-            # (1) We're passing student ID to xmodule.
-            # (2) There aren't bins of students.  -- we only want 10 or 20 randomizations, and want to assign students
-            # to these bins, and may not want cohorts.  So e.g. hash(your-id, problem_id) % num_bins.
-            #     - analytics really needs small number of bins.
-            self.seed = system.id
+        elif self.rerandomize == "per_student" and hasattr(self.system, 'seed'):
+            # see comment on randomization_bin
+            self.seed = randomization_bin(system.seed, self.location.url)
         else:
             self.seed = None
 

common/lib/xmodule/xmodule/randomize_module.py

@@ -0,0 +1,121 @@
+import json
+import logging
+import random
+
+from xmodule.mako_module import MakoModuleDescriptor
+from xmodule.x_module import XModule
+from xmodule.xml_module import XmlDescriptor
+from xmodule.modulestore import Location
+from xmodule.seq_module import SequenceDescriptor
+
+from pkg_resources import resource_string
+
+log = logging.getLogger('mitx.' + __name__)
+
+class RandomizeModule(XModule):
+    """
+    Chooses a random child module.  Chooses the same one every time for each student.
+
+     Example:
+     <randomize>
+     <problem url_name="problem1" />
+     <problem url_name="problem2" />
+     <problem url_name="problem3" />
+     </randomize>
+
+    User notes:
+
+      - If you're randomizing amongst graded modules, each of them MUST be worth the same
+        number of points.  Otherwise, the earth will be overrun by monsters from the
+        deeps.  You have been warned.
+
+    Technical notes:
+      - There is more dark magic in this code than I'd like.  The whole varying-children +
+        grading interaction is a tangle between super and subclasses of descriptors and
+        modules.
+"""
+
+    def __init__(self, system, location, definition, descriptor,
+                 instance_state=None, shared_state=None, **kwargs):
+        XModule.__init__(self, system, location, definition, descriptor,
+                         instance_state, shared_state, **kwargs)
+
+        # NOTE: calling self.get_children() creates a circular reference--
+        # it calls get_child_descriptors() internally, but that doesn't work until
+        # we've picked a choice
+        num_choices = len(self.descriptor.get_children())
+
+        self.choice = None
+        if instance_state is not None:
+            state = json.loads(instance_state)
+            self.choice = state.get('choice', None)
+            if self.choice > num_choices:
+                # Oops.  Children changed. Reset.
+                self.choice = None
+
+        if self.choice is None:
+            # choose one based on the system seed, or randomly if that's not available
+            if num_choices > 0:
+                if system.seed is not None:
+                    self.choice = system.seed % num_choices
+                else:
+                    self.choice = random.randrange(0, num_choices)
+
+        if self.choice is not None:
+            self.child_descriptor = self.descriptor.get_children()[self.choice]
+            # Now get_children() should return a list with one element
+            log.debug("children of randomize module (should be only 1): %s",
+                      self.get_children())
+            self.child = self.get_children()[0]
+        else:
+            self.child_descriptor = None
+            self.child = None
+
+
+    def get_instance_state(self):
+        return json.dumps({'choice': self.choice})
+
+
+    def get_child_descriptors(self):
+        """
+        For grading--return just the chosen child.
+        """
+        if self.child_descriptor is None:
+            return []
+
+        return [self.child_descriptor]
+
+
+    def get_html(self):
+        if self.child is None:
+            # raise error instead?  In fact, could complain on descriptor load...
+            return "<div>Nothing to randomize between</div>"
+
+        return self.child.get_html()
+
+    def get_icon_class(self):
+        return self.child.get_icon_class() if self.child else 'other'
+
+    
+class RandomizeDescriptor(SequenceDescriptor):
+    # the editing interface can be the same as for sequences -- just a container
+    module_class = RandomizeModule
+
+    filename_extension = "xml"
+
+    stores_state = True
+
+    def definition_to_xml(self, resource_fs):
+        xml_object = etree.Element('randomize')
+        for child in self.get_children():
+            xml_object.append(
+                etree.fromstring(child.export_to_xml(resource_fs)))
+        return xml_object
+
+    def has_dynamic_children(self):
+        """
+        Grading needs to know that only one of the children is actually "real".  This
+        makes it use module.get_child_descriptors().
+        """
+        return True
+

common/lib/xmodule/xmodule/tests/test_randomize_module.py

@@ -0,0 +1,55 @@
+import unittest
+from time import strptime
+from fs.memoryfs import MemoryFS
+
+from mock import Mock, patch
+
+from xmodule.modulestore.xml import ImportSystem, XMLModuleStore
+
+
+ORG = 'test_org'
+COURSE = 'test_course'
+
+START = '2013-01-01T01:00:00'
+
+
+from test_course_module import DummySystem as DummyImportSystem
+from . import test_system
+
+
+class RandomizeModuleTestCase(unittest.TestCase):
+    """Make sure the randomize module works"""
+    @staticmethod
+    def get_dummy_course(start):
+        """Get a dummy course"""
+
+        system = DummyImportSystem(load_error_modules=True)
+
+        def to_attrb(n, v):
+            return '' if v is None else '{0}="{1}"'.format(n, v).lower()
+
+        start_xml = '''
+         <course org="{org}" course="{course}"
+                graceperiod="1 day" url_name="test"
+                start="{start}"
+                >
+            <chapter url="hi" url_name="ch" display_name="CH">
+                <randomize url_name="my_randomize">
+                <html url_name="a" display_name="A">Two houses, ...</html>
+                <html url_name="b" display_name="B">Three houses, ...</html>
+                </randomize>
+            </chapter>
+         </course>
+         '''.format(org=ORG, course=COURSE, start=start)
+
+        return system.process_xml(start_xml)
+
+    def test_import(self):
+        """
+        Just make sure descriptor loads without error
+        """
+        descriptor = self.get_dummy_course(START)
+
+    # TODO: add tests that create a module and check.  Passing state is a good way to
+    # check that child access works...
+

common/lib/xmodule/xmodule/vertical_module.py

@@ -48,3 +48,5 @@ class VerticalDescriptor(SequenceDescriptor):
     js = {'coffee': [resource_string(__name__, 'js/src/vertical/edit.coffee')]}
     js_module_name = "VerticalDescriptor"
         
+    # TODO (victor): Does this need its own definition_to_xml method?  Otherwise it looks
+    # like verticals will get exported as sequentials...