Figuring out the behaviour of the neurons could take decades, although I have no doubt that people will eventually. And simulating a whole fruit fly body seems like it’s going to be out of reach for a very long time.
It has approximate weights. Neuron connection strength is determined by the number of synapses (1-100s, sometimes 1000s), the type of synapse neurotransmitter, and the number of receptors. The connectome has 1 and 2 and is only missing 3. The number of receptors may not even be that important- the fact that the number of synapses is important may well mean the number of receptors is unreliable.
Neurons also don't transmit scalars to each other. The synapse is stimulate by frequency of action potentials much more than strength.
> And it doesn’t have a body.
It does have nervous connections outside the brain. That behavior is not as complex.
> Figuring out the behaviour of the neurons could take decades
Neurons are not that complex in terms of matching in->out behavior. Since spiking is frequency-based, you can verify it quite well by ensuring the frequency of spikes in->out matches; you can even measure single neurons with implanted electrodes. You don't need so much precision to see individual spikes, since the size of the spikes does not matter much at all.
Long term potentiation also makes measuring individual neuron strength even less important- if you model potentiation correctly, then over time you'll converge accurately as understimulated connections weaken and vice versa.
The real issue is we have barely any clue how potentiation works and can't model it well at all. It's very important to brain behavior and most of the interesting things brains do. Its kind of an issue.
But the astrocytes are dynamically modulating the signal at the synapse, it doesn't seem like we really know "the" weight.
It's also not just frequency, but "shape" (for lack of a better word) of incoming inputs that matters, as such there is a very wide variety of spiking patterns that certain cells exhibit, like chopper cells.