Uncaught TypeError: Cannot read property 'length' of undefined

[mdecandia]

Problem Inspector fails to start up for the below problem. It shows a blue screen and an error in the console. Unfortunately, I have not found what exactly causes the issue in this problem.

Problem:

import sys
import dimod
import dwave.inspector
from minorminer import find_embedding
from dwave.cloud import Client
from dwave.embedding import embed_bqm, unembed_sampleset
from dwave.embedding.utils import edgelist_to_adjacency
import networkx as nx
import dwave_networkx as dnx
import numpy as np
from dwave.system import DWaveSampler, EmbeddingComposite,FixedEmbeddingComposite

sampler = EmbeddingComposite(DWaveSampler(solver=dict(qpu=True)))
Q = {('x', 'x'): -1, ('x', 'z'): 2, ('z', 'x'): 0, ('z', 'z'): -1}

sampler_embedded = FixedEmbeddingComposite(sampler, {'x': [4], 'z': [0, 128, 256, 384, 512, 640, 768]})
sampleset = sampler_embedded.sample_qubo(Q, num_reads=5000, chain_strength=1)
sampleset.info["embedding"] = {'x': [4], 'z': [0, 128, 256, 384, 512, 640, 768]}

dwave.inspector.show(dimod.BQM.from_qubo(Q), sampleset, sampler_embedded)

Console Error:

Uncaught TypeError: Cannot read property 'length' of undefined
    at main.8f0edd8b.chunk.js:1
    at main.8f0edd8b.chunk.js:1
    at Map.forEach (<anonymous>)
    at c.iterateNodes (main.8f0edd8b.chunk.js:1)
    at Object.layoutVars (main.8f0edd8b.chunk.js:1)
    at Object.<anonymous> (main.8f0edd8b.chunk.js:1)
    at v.applyLayoutFunction (main.8f0edd8b.chunk.js:1)
    at main.8f0edd8b.chunk.js:1
    at main.8f0edd8b.chunk.js:1
    at Array.forEach (<anonymous>)

Screenshot:

[randomir]

The problem here boils down to nested embedding composites. First you define:

sampler = EmbeddingComposite(DWaveSampler(...))

and then:

sampler_embedded = FixedEmbeddingComposite(sampler, ...)

Not sure if that was your intent. If one composite is removed (probably makes sense to remove the first one), then everything works (and you can avoid manually setting the embedding on sampleset, that's not needed).

The lesson learnt is we need to compose embeddings returned by embedding composites when return_embedding=True, and when embedding composites are nested. Thus, I'll open an issue on dwave-system.

[arcondello]

One other approach that was discussed back in the requirements stage would be to give the inspector the ability to show multiple intermediate BQMs. So logical -> intermdiate -> source. This deemed too much work for R1 but in the context of debugging it would (IMO) be more useful than composed embeddings, in that embedding warnings etc can be embedding specific. Of course there are another whole class of warnings that come out of embedding interactions, in which case the composed embeddings are useful 🤷‍♂

[randomir]

Yup, that's the obvious next step after plot-style inspector -- the dashboard-style inspector, where user would be able to browse all captured data and inspect it...

[mdecandia]

Thanks! My bad. That was somewhat unintentional. And it does work when removing the EmbeddingComposite. Shall I close this issue or wait for that one to be resolved?

Compose embedding when returning it #251

[randomir]

It's not clear how to handle nested embedding composites transparently (see comments on the linked dwave-system issue).

I think the best solution will be the dashboard-style inspector, where user will be able to browse problems/solutions, including intermediate steps. But that's not going to be implemented anytime soon.

So, I'd close this one in favor of #40.

[mdecandia]

That dashboard-style inspector solution sounds pretty cool. But yeah, I don't think we'll see that anytime soon.

Closing ticket.