Re: [UrbanSim-Users] HLCM, use sample with replacement

Brian,
In term of choice model, sampling with replacement would mean to include
possible duplicates in households' sampled alternative set, which I don't
think make much sense in this case. The default
opus_core.sampler.weight_sampler samples from the pool of potential choices
and allows the same choice to appear in different households' alternative
set, but not replacement in any given household's alternative set.
(Although when it runs out of unique choices, the sampler will try to sample
with replacement to achieve the choice_set size.) Should you want this
changed, you may model opus_core/sampler/weighted_sampler.py and write your
own sampler.

Hope this helps,
Liming.

On Thu, Mar 6, 2008 at 2:11 PM, brian voigt <brian.voigt_at_uvm.edu> wrote:

> thanks Liming. Can you tell me where I can change from the existing
> sampling method to the sample with replacement? Does sample with replacement
> mean that if a unit is not selected by a household that it is then returned
> to the pool of potential choices (and therefore available to another
> household via their choice set)?
> brian
>
> Liming Wang wrote:
>
> Brian,
> This is likely caused by running out vacant residential units. Because
> HLCM samples gridcells weighted by vacant_residential_units, this will
> create a zero-division when the weight is zero. Either because of strict
> development constraints or sudden increase of households, the developer
> model is not building enough residential units for households for the
> simulation year.
>
> Liming.
>
> On Thu, Mar 6, 2008 at 10:11 AM, Brian Miles <Brian.Miles_at_uvm.edu> wrote:
>
> >
> > Hello,
> >
> > We're seeing the following error in the seventh iteration of our HLCM:
> >
> > HLCM chunk 4 out of 12.: started on Thu Mar 06 08:07:45 2008
> > Number of agents in this chunk: 56
> > urbansim.gridcell.vacant_residential_units
> >
> > urbansim.gridcell.number_of_households...........0.0 sec
> > urbansim.gridcell.vacant_residential_units:
> > completed...0.0 sec
> > Available capacity: 0 units.
> > Sampling locations ...
> > WARNING: weight_array sums to 0 or less
> > WARNING: weight array dosen't have enough non-zero
> > counts, use sample with replacement
> > WARNING: prob_array doesn't sum up to 1, and is
> > normalized. Sum: 0.0
> > HLCM chunk 4 out of 12.:
> > completed.......................0.0 sec
> >
> > (full stack trace is below)
> >
> > We were able to get our simulation past this error and to run beyond
> > the seventh year, all the way to the 10th, by adding five residential
> > units to all gridcells with non-zero residential units.
> >
> > But we don't know what the error "weight array dosen't have enough non-
> > zero counts, use sample with replacement"--thrown by
> > opus_core.samplers.weighted_sampler--means. It seems to be telling us
> > to try setting some option, but I'm not sure.
> >
> > How should we interpret this error?
> >
> > Thanks,
> >
> > Brian
> >
> >
> > Number of unplaced agents: 45 (in 2 iterations)
> > HLCM chunk 3 out of 12.:
> > completed.......................0.6 sec
> > HLCM chunk 4 out of 12.: started on Thu Mar 06
> > 08:07:45 2008
> > Number of agents in this chunk: 56
> > urbansim.gridcell.vacant_residential_units
> >
> > urbansim.gridcell.number_of_households...........0.0 sec
> > urbansim.gridcell.vacant_residential_units:
> > completed...0.0 sec
> > Available capacity: 0 units.
> > Sampling locations ...
> > WARNING: weight_array sums to 0 or less
> > WARNING: weight array dosen't have enough non-zero
> > counts, use sample with replacement
> > WARNING: prob_array doesn't sum up to 1, and is
> > normalized. Sum: 0.0
> > HLCM chunk 4 out of 12.:
> > completed.......................0.0 sec
> > Running Household Location Choice Model (from
> > urbansim.models.household_location_choice_model): completed...18.8 sec
> > Simulate year 1997: completed.............................1
> > min, 3.7 sec
> > Closing log file: C://urbansim_cache
> > \run_63.2008_03_06_07_59\year_1997_log.txt
> > Starting simulation for year 1997: completed..................1
> > min, 3.7 sec
> > Start simulation run: completed...................................1
> > min, 3.7 sec
> > Closing log file: C://urbansim_cache
> > \run_63.2008_03_06_07_59\run_multiprocess.log
> > Traceback (most recent call last):
> > File "C:\opusworkspace-svn\urbansim\model_coordinators
> > \model_system.py", line 532, in <module>
> > s.run(resources)
> > File "C:\opusworkspace-svn\urbansim\model_coordinators
> > \model_system.py", line 135, in run
> >
> > write_datasets_to_cache_at_end_of_year
> > =write_datasets_to_cache_at_end_of_year)
> > File "C:\opusworkspace-svn\urbansim\model_coordinators
> > \model_system.py", line 299, in _run_year
> > self.vardict[outputvar] = self.do_process(locals())
> > File "C:\opusworkspace-svn\urbansim\model_coordinators
> > \model_system.py", line 377, in do_process
> > return eval(ev)
> > File "<string>", line 1, in <module>
> > File "C:\opusworkspace-svn\opus_core\model.py", line 48, in
> > logged_run_method
> > results = run_method(*req_args, **opt_args)
> > File "C:\opusworkspace-svn\opus_core\configurable.py", line 38, in
> > config_run_method
> > results = run_method(*req_args, **opt_args)
> > File "C:\opusworkspace-svn\urbansim\models
> > \agent_location_choice_model.py", line 88, in run
> > agents_index[unplaced], chunk_specification, debuglevel=debuglevel)
> > File "C:\opusworkspace-svn\urbansim\models
> > \location_choice_model.py", line 123, in run
> > debuglevel=debuglevel)
> > File "C:\opusworkspace-svn\opus_core\choice_model.py", line 142, in
> > run
> > specification=specification, coefficients=coefficients)
> > File "C:\opusworkspace-svn\opus_core\chunk_model.py", line 72, in run
> > dataset, **kwargs).astype(result_array_type)
> > File "C:\opusworkspace-svn\urbansim\models
> > \agent_location_choice_model.py", line 101, in run_chunk
> > result = LocationChoiceModel.run_chunk(self, agents_index,
> > agent_set, specification, coefficients)
> > File "C:\opusworkspace-svn\urbansim\models
> > \location_choice_model.py", line 144, in run_chunk
> > choices = ChoiceModel.run_chunk(self,agents_index, agent_set,
> > specification, coefficients)
> > File "C:\opusworkspace-svn\opus_core\choice_model.py", line 152, in
> > run_chunk
> > index = self.get_choice_index(agent_set, agents_index, agentsubset)
> > File "C:\opusworkspace-svn\urbansim\models
> > \location_choice_model.py", line 270, in get_choice_index
> > weight=self.weights, resources=self.run_config)
> > File "C:\opusworkspace-svn\opus_core\configurable.py", line 38, in
> > config_run_method
> > results = run_method(*req_args, **opt_args)
> > File "C:\opusworkspace-svn\opus_core\samplers\weighted_sampler.py",
> > line 103, in run
> > replace=replace, return_indices=True )
> > File "C:\opusworkspace-svn\opus_core\sampling_toolbox.py", line 284,
> > in prob2dsample
> > cum_prob = ncumsum(p_array)
> > File "C:\opusworkspace-svn\opus_core\misc.py", line 515, in ncumsum
> > str(prob_array.sum(axis=axis, dtype=dtype))
> > ValueError: The probability array must sum up to 1. It is -1.#IND
> > Running UrbanSim for year 1997 in new process: completed..........1
> > min, 5.5 sec
> > Traceback (most recent call last):
> > File "start_run.py", line 84, in <module>
> > run_manager.run_run(config, run_as_multiprocess =
> > run_as_multiprocess)
> > File "C:\opusworkspace-svn\opus_core\services\run_server
> > \run_manager.py", line 183, in run_run
> > raise SimulationRunError
> > opus_core.services.run_server.run_manager.SimulationRunError
> > _______________________________________________
> > Users mailing list
> > Users_at_urbansim.org
> > http://www.urbansim.org/mailman/listinfo/users
> >
>
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Received on Tue Mar 11 2008 - 12:23:09 PDT