Is AGI just a question of scale now – AGI part-5

Read two articles over the past month or so. The more recent one was an Economist article (AI enters the industrial age, paywall) and the other was A generalist agent (from Deepmind). The Deepmind article was all about the training of Gato, a new transformer deep learning model trained to perform well on 600 separate task arenas from image captioning, to Atari games, to robotic pick and place tasks.

And then there was this one tweet from Nando De Frietas, research director at Deepmind:

Someone’s opinion article. My opinion: It’s all about scale now! The Game is Over! It’s about making these models bigger, safer, compute efficient, faster at sampling, smarter memory, more modalities, INNOVATIVE DATA, on/offline, … 1/N

I take this to mean that AGI is just a matter of more scale. Deepmind and others see the way to attain AGI is just a matter of throwing more servers, GPUs and data at the training the model.

We have discussed AGI in the past (see part-0 [ish], part-1 [ish], part-2 [ish], part-3ish and part-4 blog posts [We apologize, only started numbering them at 3ish]). But this tweet is possibly the first time we have someone in the know, saying they see a way to attain AGI.

Transformer models

It’s instructive from my perspective that, Gato is a deep learning transformer model. Also the other big NLP models have all been transformer models as well.

Gato (from Deepmind), SWITCH Transformer (from Google), GPT-3/GPT-J (from OpenAI), OPT (from meta), and Wu Dai 2.0 (from China’s latest supercomputer) are all trained on more and more text and image data scraped from the web, wikipedia and other databases.

Wikipedia says transformer models are an outgrowth of RNN and LSTM models that use attention vectors on text. Attention vectors encode, into a vector (matrix), all textual symbols (words) prior to the latest textual symbol. Each new symbol encountered creates another vector with all prior symbols plus the latest word. These vectors would then be used to train RNN models using all vectors to generate output.

The problem with RNN and LSTM models is that it’s impossible to parallelize. You always need to wait until you have encountered all symbols in a text component (sentence, paragraph, document) before you can begin to train.

Instead of encoding this attention vectors as it encounters each symbol, transformer models encode all symbols at the same time, in parallel and then feed these vectors into a DNN to assign attention weights to each symbol vector. This allows for complete parallelism which also reduced the computational load and the elapsed time to train transformer models.

And transformer models allowed for a large increase in DNN parameters (I read these as DNN nodes per layer X number of layers in a model). GATO has 1.2B parameters, GPT-3 has 175B parameters, and SWITCH Transformer is reported to have 7X more parameters than GPT-3 .

Estimates for how much it cost to train GPT-3 range anywhere from $10M-20M USD.

AGI will be here in 10 to 20 yrs at this rate

So if it takes ~$15M to train a 175B transformer model and Google has already done SWITCH which has 7-10X (~1.5T) the number of GPT-3 parameters. It seems to be an arms race.

If we assume it costs ~$65M (~2X efficiency gain since GPT-3 training) to train SWITCH, we can create some bounds as to how much it will cost to train an AGI model.

By the way, the number of synapses in the human brain is approximately 1000T (See Basic NN of the brain, …). If we assume that DNN nodes are equivalent to human synapses (a BIG IF), we probably need to get to over 1000T parameter model before we reach true AGI.

So my guess is that any AGI model lies somewhere between 650X to 6,500X parameters beyond SWITCH or between 1.5Q to 15Q model parameters.

If we assume current technology to do the training this would cost $40B to $400B to train. Of course, GPUs are not standing still and NVIDIA’s Hopper (introduced in 2022) is at least 2.5X faster than their previous gen, A100 GPU (introduced in 2020). So if we waited a 10 years, or so we might be able to reduce this cost by a factor of 100X and in 20 years, maybe by 10,000X, or back to where roughly where SWITCH is today.

So in the next 20 years most large tech firms should be able to create their own AGI models. In the next 10 years most governments should be able to train their own AGI models. And as of today, a select few world powers could train one, if they wanted to.

Where they get the additional data to train these models (I assume that data counts would go up linearly with parameter counts) may be another concern. However, I’m sure if you’re willing to spend $40B on AGI model training, spending a few $B more on data acquisition shouldn’t be a problem.

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At the end of the Deepmind article on Gato, it talks about the need for AGI safety in terms of developing preference learning, uncertainty modeling and value alignment. The footnote for this idea is the book, Human Compatible (AI) by S. Russell.

Preference learning is a mechanism for AGI to learn the “true” preference of a task it’s been given. For instance, if given the task to create toothpicks, it should realize the true preference is to not destroy the world in the process of making toothpicks.

Uncertainty modeling seems to be about having AI assume it doesn’t really understand what the task at hand truly is. This way there’s some sort of (AGI) humility when it comes to any task. Such that the AGI model would be willing to be turned off, if it’s doing something wrong. And that decision is made by humans.

Deepmind has an earlier paper on value alignment. But I see this as the ability of AGI to model human universal values (if such a thing exists) such as the sanctity of human life, the need for the sustainability of the planet’s ecosystem, all humans are created equal, all humans have the right to life, liberty and the pursuit of happiness, etc.

I can see a future post is needed soon on Human Compatible (AI).

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Better autonomous drone flying with Neural-Fly

Read an article the other day on Neural-Fly (see: Rapid adaptation of deep learning teaches drones to survive any weather) based on research out of CalTech documented in a paper is ScienceRobotics (see: Neural-Fly enables rapid learning for agile flight in strong winds, behind paywall).

Essentially they have trained two neural networks (NN) at the same time and computed an adaptation coefficient matrix (with linear multipliers to compensate for wind speed). The first NN is trained to understand the wind invariant flight characteristics of a drone in wind and the second is trained to the predict the class of wind the drone is flying in (or wind index). These two plus the adaptation control matrix coefficients are used to predict the resultant force on drone flight in wind.

In a CalTech article on the research (see: Rapid Adaptation of Deep Learning Teaches Drones to Survive Any Weather) at the bottom is a YouTube video that shows how well the drone can fly in various wind conditions (up to 27mph).

The data to train the two NNs and compute the adaptation matrix coefficients come from CalTech wind tunnel results with their custom built drone (essentially an RPi4 added to a pretty standard drone) doing random trajectories under different static wind conditions.

The two NNs and the adaptation control matrix functionality run on a Raspberry Pi 4 (RPi4) that’s added to a drone they custom built for the test vehicle. The 2 NNs and the adaptation control tracking are used in the P-I-D (proportional-integral-derivative) controller for drone path prediction. The Neural-Fly 2 NNs plus the adaptation functionality effectively replaces the residual force prediction portion of Integral section of the P-I-D controller.

The wind invariant neural net has 5 layers with relatively few parameters per layer. The wind class prediction neural network has 3 layers and even fewer parameters. Together these two NNs plus the adaptation coefficient provides real time resultant force predictions on the drone which can be fed into the drone controller to control drone flight. All being accomplished, in real time, on an RPi4.

The adaption factor matrix is also learned during 2 NN training. And this is what’s used in the NF-Constant results below. But the key is that the linear factors (adaptation matrix) are updated (periodically) during actual drone flight by sampling the measured actual force and predicated force on the drone. The adaption matrix coefficients are updated using a least squares estimation fit.

In the reports supplemental information, the team showed a couple of state of the art adaptation approaches to problem of drone flight in wind. In the above chart the upper section is the x-axis wind effect and the lower portion is the z-axis wind effect and f (grey) is the actual force in that direction and f-hat (red) is the predicted force. The first column represents results from a normal integral controller. The next two columns are state of the art approaches (INDI and L1, see paper references) to the force prediction using adaptive control. If you look closely at these two columns, and compare the force prediction (in red) and the actual force (in grey), the force prediction always lags behind the actual force.

The next three columns show Neural-Fly constant (Neural-Fly with a constant adaptive control matrix, not being updated during flight), Neural-Fly-transfer (Using the NN trained on one drone and applying it’s adaptation to another drone in flight) and Neural-Fly. Neural-Fly constant also shows a lag between the predicted force and the actual force. But the Neural-Fly Transfer and Neural-Fly reduce this lag considerably.

The measurement for drone flight accuracy is tracking positional error. That is the difference between the desired position and its actual position over a number of trajectories. As shown in the chart tracking error decreased from 5.6cm to ~4 cm at a wind speed of 4.2m/s (15.1km/h or 9.3mph). Tracking error increases for wind speeds that were not used in training and for NF-transfer but in all wind speeds the tracking error is better with Neural-Fly than with any other approach.

Pretty impressive results from just using an RPi4.

[The Eds. would like to thank the CalTech team and especially Mike O’Connell for kindly answering our many questions on Neural-Fly.]

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Go big or go home for robust DNNs

Read a recent article Computer Scientists Prove why Bigger NNs do better discussing scientific research that proved a Universal Law of Robustness via Isoperimetry. This speaks to the perturbability of AI deep learning neural networks (DNN) and how not reduce it. But also applies to many other solutions to diverse multi-dimensional data problems.

Mathmatical Robustness

For AI ML DNN’s, we often witnesssupposedly well trained DNN models that do very well for classifications of examples of data similar to their training data but fail miserably on data that’s outside their training data.

Mathematicians call this attribute robustness and can measure this on a mapping function using a Lipschitz constant. One can consider this as a measure of variability of mapping from one set to another or in the case of DNNs, lack of robustness in classifications means they fail on relatively minor changes to input data.

Most serious AI researchers have empirically discovered that bigger DNNs work better and are more robust than smaller networks. There’s been somewhat of a conundrum as to why DNNs need to get bigger to properly generalize.

Universal Low of Robustness

What the researchers have proved is that in order to achieve some arbitrary level of robustness for a mapping function like DNNs, one needs many more parameters than expected the training data elements would indicate

For example, with the MNIST handwritten digit classification problem, models with 10**5 parameters to 10**6 parameters are required to achieve a 90% and 95% accuracy, respectively. But MNIST training data is 60K examples (10**4). Why should a MNIST DNN classification model need more than 10**4 parameters to achieve 100% accurate?

Author’s MNIST model with 688K parameters

From what we all learned in high school maths, to solve a function with N variables one needs N equations. This would lead one to believe that MNIST DNNs (essentially solving classification equations) should only need 60K or 10**4 parameters. But real DNNs to solve MNIST need more than that.

Looking at it in 2D. If one has two points, (x,y) for point A that maps to another (x,y) point B, one should only need to know one of the points and the slope of the line that connects them, or two parameters: point A (or B) and line slope.

Now with MNIST data that maps handwritten digits to one of 10 digits, we have essentially 10 possibilities being mapped from 60K samples. At best, we should need to know the 60K initial points in this image data space and their slope to the 10 digits they represent. Again something that approaches 60K pairs of parameters: one for the image point and one for the slope. But why doesn’t a MNIST model with 60K parameters achieve 100% accuracy.

I won’t claim to understand the math but what the researchers seem to be saying is that in order to have a relatively smooth mapping from the image space to the digit space one has to have 10**4 parameters X the dimensionality of the data. In this case, for MNIST, the dimensionality of the data is related to image size of 28X28, 0..255 grey scale pixel images. The image space alone would be on the order of 10**5. So multiplying this by the size of the training data, the researchers estimate that the number of parameters should be 10**9 to be 100% accurate.

Although, the researchers say that the data dimensionality of the MNIST images are probably not 10**5 (how they concluded this is not evident). As such, they believe one shouldn’t need 10**9 parameters to reach 100% proper classifications. They say it’s probably 1 or 2 orders of magnitude less, because not all of the image data space is populated. So if we use 10**3 as an estimate of the effective data dimensionality, they would estimate that one would need 10**7 parameter DNN to reach 100% accuracy on MNIST data.

The author’s MNIST model achieved a 99.2% accuracy after training for 15 Epochs, batch size=5. Although 688K parameters is not quite 10**6 parameters, it’s close. Unclear why one would need another factor of 10, but getting that extra 0.8% accuracy (to 100%) can be very difficult to achieve for any DNN model.

Another example, OpenAI’s GPT-3 NLP model

And OpenAI’s GPT-3 NLP model has 175B parameters. Their previous version, GPT-2, only had 1.5B parameters and they say that GPT-4 will have over a 100T parameters. The chart above shows accuracy stats for 3 versions of the GPT-3 model, one with 175B, one with 13B and another with 1.3B parameters.

According to OpenAI’s GPT-3 description, it can complete “almost any english language task” (text in ==> text out). This includes writing articles from a few prompts and text summarization.

GPT-3 was trained on almost 500B tokens (from web crawls to wikipedia dumps). Each token probably represents an english word or word phrase. According to the universal law, 175B parameters would not be sufficient. Probably why GPT-3 in the above chart didn’t reach 70%^ accuracy.

Probably would need at least another 3 orders of magnitude to get there or 175T parameters. Maybe with GPT-4, I can have it start writing my blog posts.

I don’t know about you, but I’m going to need more GPUs for my (home) AI lab.

Photo Credit(s)

AI navigation goes with the flow

Read an article the other day (Engineers Teach AI to Navigate Ocean with Minimal Energy) about a simulated robot that was trained to navigate 2D turbulent water flow to travel between locations. They used a combination reinforcement learning with a DNN derived policy. The article was reporting on a Nature Communications open access paper (Learning efficient navigation in vortical flow fields).

The team was attempting to create an autonomous probe that could navigate the ocean and other large bodies of water to gather information. I believe ultimately the intent was to provide the navigational smarts for a submersible that could navigate terrestrial and non-terrestrial oceans.

One of the biggest challenges for probes like this is to be able to navigate turbulent flow without needing a lot of propulsive power and using a lot of computational power. They said that any probe that could propel itself faster than the current could easily travel wherever it wanted but the real problem was to go somewhere with lower powered submersibles.. As a result, they set their probe to swim at a constant speed at 80% of the overall simulated water flow.

Even that was relatively feasible if you had unlimited computational power to train and inference with but trying to do this on something that could fit in a small submersible was a significant challenge. NLP models today have millions of parameters and take hours to train with multiple GPU/CPU cores in operation and lots of memory Inferencing using these NLP models also takes a lot of processing power.

The researchers targeted the computational power to something significantly smaller and wished to train and perform real time inferencing on the same hardware. They chose a “Teensy 4.0 micro-controller” board for their computational engine which costs under $20, had ~2MB of flash memory and fit in a space smaller than 1.5″x1.0″ (38.1mm X 25.4mm).

The simulation setup

The team started their probe turbulent flow training with a cylinder in a constant flow that generated downstream vortices, flowing in opposite directions. These vortices would travel from left to right in the simulated flow field. In order for the navigation logic to traverse this vortical flow, they randomly selected start and end locations on different sides.

The AI model they trained and used for inferencing was a combination of reinforcement learning (with an interesting multi-factor reward signal) and a policy using a trained deep neural network. They called this approach Deep RL.

For reinforcement learning, they used a reward signal that was a function of three variables: the time it took, the difference in distance to target and a success bonus if the probe reached the target. The time variable was a penalty and was the duration of the swim activity. Distance to target was how much the euclidean distance between the current probe location and the target location had changed over time. The bonus was only applied when the probe was in close proximity to the target location, The researchers indicated the reward signal could be used to optimize for other values such as energy to complete the trip, surface area traversed, wear and tear on propellers, etc.

For the reinforcement learning state information, they supplied the probe and the target relative location [Difference(Probe x,y, Target x,y)], And whatever sensor data being tested (e.g., for the velocity sensor equipped probe, the local velocity of the water at the probe’s location).

They trained the DNN policy using the state information (probe start and end location, local velocity/vorticity sensor data) to predict the swim angle used to navigate to the target. The DNN policy used 2 internal layers with 64 nodes each.

They benchmarked the Deep RL solution with local velocity sensing against a number of different approaches. One naive approach that always swam in the direction of the target, one flow blind approach that had no sensors but used feedback from it’s location changes to train with, one vorticity sensor approach which sensed the vorticity of the local water flow, and one complete knowledge approach (not shown above) that had information on the actual flow at every location in the 2D simulation

It turned out that of the first four (naive, flow-blind, vorticity sensor and velocity sensor) the velocity sensor configured robot had the highest success rate (“near 100%”).

That simulated probe was then measured against the complete flow knowledge version. The complete knowledge version had faster trip speeds, but only 18-39% faster (on the examples shown in the paper). However, the knowledge required to implement this algorithm would not be feasible in a real ocean probe.

More to be done

They tried the probes Deep RL navigation algorithm on a different simulated flow configuration, a double gyre flow field (sort of like 2 circular flows side by side but going in the opposite directions).

The previously trained (on cylinder vortical flow) Deep RL navigation algorithm only had a ~4% success rate with the double gyre flow. However, after training the Deep RL navigation algorithm on the double gyre flow, it was able to achieve a 87% success rate.

So with sufficient re-training it appears that the simulated probe’s navigation Deep RL could handle different types of 2D water flow.

The next question is how well their Deep RL can handle real 3D water flows, such as idal flows, up-down swells, long term currents, surface wind-wave effects, etc. It’s probable that any navigation for real world flows would need to have a multitude of Deep RL trained algorithms to handle each and every flow encountered in real oceans.

However, the fact that training and inferencing could be done on the same small hardware indicates that the Deep RL could possibly be deployed in any flow, let it train on the local flow conditions until success is reached and then let it loose, until it starts failing again. Training each time would take a lot of propulsive power but may be suitable for some probes.

The researchers have 3D printed a submersible with a Teensy microcontroller and an Arduino controller board with propellers surrounding it to be able to swim in any 3D direction. They have also constructed a water tank for use for in real life testing of their Deep RL navigation algorithms.

Picture credit(s):

The problem with smarter robots

Read an article the other week about how Deepmind (at Google) is approaching the training of robotics using simulation, reinforcement learning, elastic weights, knowledge distillation and progressive learning.

It seems relatively easy to train a robot to handle some task like grabbing or walking. But doing so can take an awfully long time. If you want to try to train a robot to grab something and put it someplace. You can have it start out making some random movements of its arm, wrist and fingers (if they have such things) and then use reinforcement learning to help it improve its movements over time.

But if each grab attempt takes 10 seconds, using reinforcement learning may take 10,000 attempts before it starts to make any significant progress and perhaps another 20,000-50,000 more to get expert at it. Let’s see 60K *10 seconds is 10,000 minutes or ~170 hours. And that’s just one object pick and place. But then maybe you would like to grab different parts and maybe place them in different locations. All these combinations start adding up.

And of course doing 1000s of movements will wear out gears, motors, mechanisms etc. If only this could all be done in electronic simulations. Then assuming the simulations are accurate enough the whole thing could be done in a matter of hours without wearing anything out. Enter robot simulators such as NVIDIA Isaac Sim, OpenAI RoboSchool/PyBullet

But the problems with simulation are …

Simulations are getting more accurate but at some point their accuracy defeats its purpose because the real world is always noisy, windy and not as deterministic as any simulation. One researcher said you could conceivable have a two armed robot be trained to throw all of a cell phones components up into the air and they will all land in their proper places, proper orientations. But in the real world this could never actually happen, or if it did, it could only happen once.

Hurricane Ike - 2008/09/12 - 21:26 UTC by CoreBurn (cc) (from Flickr)
Hurricane Ike – 2008/09/12 – 21:26 UTC by CoreBurn (cc) (from Flickr)

Weather researchers have been dealing with this problem in spades for a long time. There appears to be a fundamental limit to how far in advance we can predict weather and it’s due to the accuracy with which sensors operate and the complexity of feedback loops between the atmosphere, oceans, landforms, etc. So at a fundamental level, simulations can never be completely accurate. But they can be better.

Today’s weather simulations we see on TV/radio use models that average a number of distinct simulations, where sensor information has been slightly and randomly modified. Something similar could be done for robotic simulation environments, to make them more realistic.

But there are other problems with training robots to do lots of tasks.

Forget me not…

AI deep learning and reinforcement learning algorithms are great when charged with learning a single task, but having it learn multiple tasks is much harder to do. Because each task requires its own deep neural network (DNN) and if you train a DNN on one task and then try to train in on a another task, it forgets all the learnings from the original task. Researchers call this catastrophic forgetting.

One way researchers have dealt with this problem is to effectively freeze certain DNN nodes from having their weights changed during subsequent training rounds and leave others flexible or changeable. One can see this when one trains an image recognition DNN to classify different objects by importing a well trained object classifier and freezing all of it’s layers except the top one or two and then training these layers to classify new objects.

This works well but you have effectively changed the DNN to forget the original object classification training and replaced it with a new one. One solution to this approach is to have multiple passes of training, after each one, certain nodes and connections (of importance to that particular task) are selectively frozen. This works well for a limited number of different tasks but over time all nodes become frozen which means that no more learning can take place. Researchers call this approach to the catastrophic forgetting problem elastic weights.

One way to get around the all nodes frozen issue in elastic weights is to have multiple NNs. One which is trained on a specific task and whose weights are frozen and then a DNN that exists alongside this one with it’s own initialized set of weights. But which uses the original DNN as part of the new DNN inputs. This effectively includes and incorporates all the previously learned knowledge into the new, combined DNN. This is called Progressive Neural Networks.

In this fashion one progressive DNN can be sequentially trained on any number of tasks each of which ends up providing input to all subsequent task training activity. Such a progressive network never forgets and can use previously learned knowledge on new tasks.

The problem with progressive DNNs is a proliferation of DNN column. one for each trained task. However there are a couple of approaches to shrinking an ensemble of DNN like progressive training creates into one that is simpler and just as effective. One way is to perturb weights in DNN nodes and see how model prediction accuracy is impacted on all its tasks. If accuracy isn’t impacted that much, then that node and all its connections could be deleted from the model with minimal impact on model accuracy.

Another approach is to use one DNN to train another. Sort of like a teacher-student. This is called Knowledge Distilation. Where one DNN is a large network (the teacher) and a smaller (student) network that is trained to mimic the teacher DNN to achieve similar accuracy. This is done by training the smaller student network to match the predictions/classifications of the larger one.

Google researchers have shown that knowledge distillation works best when the gap in the sizes of the two networks (teacher and student) aren’t that large. They have solved this problem by introducing an intermediate step (called teachers assistent). They train this TA first then use the TA to train the student.

In the above graphic, when using a teacher of size 110 and a student of size 8 the resulting accuracy suffers but if one uses an intermediate DNN, with a size 20 the resultant accuracy of the student is much closer to the teacher..

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So with realistic simulation we can train a robot to do any specific task, all using only compute resources. And using progressive DNN training, a robot could conceivably be trained to do any number of tasks. And with appropriate knowledge distillation one can reduce the DNN from progressive training into something much smaller (<10%) than the original DNN.

Want a personal robot that can clean up around your place, do the wash, cook your food and do anything else needed. You know what to do.

Swarm learning for distributed & confidential machine learning

Read an article the other week about researchers in Germany working with a form of distributed machine learning they called swarm learning (see: AI with swarm intelligence: a novel technology for cooperative analysis …) which was reporting on a Nature magazine article (see: Swarm Learning for decentralized and confidential clinical machine learning).

The problem of shared machine learning is particularly accute with medical data. Many countries specifically call out patient medical information as data that can’t be shared between organizations (even within country) unless specifically authorized by a patient.

So these organizations and others are turning to use distributed machine learning as a way to 1) protect data across nodes and 2) provide accurate predictions that uses all the data even though portions of that data aren’t visible. There are two forms of distributed machine learning that I’m aware of federated and now swarm learning.

The main advantages of federated and swarm learning is that the data can be kept in the hospital, medical lab or facility without having to be revealed outside that privileged domain BUT the [machine] learning that’s derived from that data can be shared with other organizations and used in aggregate, to increase the prediction/classification model accuracy across all locations.

How distributed machine learning works

Distributed machine learning starts with a common model that all nodes will download and use to share learnings. At some agreed to time (across the learning network), all the nodes use their latest data to re-train the common model and share new training results (essentially weights used in the neural network layers) with all other members of the learning network.

Shared learnings would be encrypted with TLS plus some form of homomorphic encryption that allowed for calculations over the encrypted data.

In both federated and swarm learning, the sharing mechanism was facilitated by a privileged block chain (apparently Etherium for swarm). All learning nodes would use this blockchain to share learnings and download any updates to the common model after sharing.

Federated vs. Swarm learning

The main difference between federated and swarm learning is that with federated learning there is a central authority that updates the model(s) and with swarm learning that processing is replaced by a smart contract executing within the blockchain. Updating model(s) is done by each node updating the blockchain with shared data and then once all updates are in, it triggers a smart contract to execute some Etherium VM code which aggregates all the learnings and constructs a new model (or at least new weights for the model). Thus no node is responsible for updating the model, it’s all embedded into a smart contract within the Etherium block chain. .

Buthow does the swarm (or smart contract) update the common model’s weights. The Nature article states that they used either a straight average or a weighted average (weighted by “weight” of a node [we assume this is a function of the node’s re-training dataset size]) to update all parameters of the common model(s).

Testing Swarm vs. Centralized vs. Individual (node) model learning

In the Nature paper, the researchers compared a central model, where all data is available to retrain the models, with one utilizing swarm learning. To perform the comparison, they had all nodes contribute 20% of their test data to a central repository, which ran the common swarm updated model against this data to compute an accuracy metric for the swarm. The resulting accuracy of the central vs swarm learning comparison look identical.

They also ran the comparison of each individual node (just using the common model and then retraining it over time without sharing this information to the swarm versus using the swarm learning approach. In this comparison the swarm learning approach alway seemed to have as good as if not better accuracy and much narrower dispersion.

In the Nature paper, the researchers used swarm learning to manage the machine learning model predictions for detecting COVID19, Leukemia, Tuberculosis, and other lung diseases. All of these used public data, which included PBMC (peripheral blood mono-nuclear cells) transcription data, whole blood transcription data, and X-ray images.

Swarm learning also provides the ability to onboard new nodes in the network. Which would supply the common model and it’s current weights to the new node and add it to the shared learning smart contract.

The code for the swarm learning can be downloaded from HPE (requires an HPE passport login [it’s free]). The code for the models and data processing used in the paper are available from github. All this seems relatively straight forward, one could use the HPE Swarm Learning Library to facilitate doing this or code it up oneself.

Photo Credit(s):

AI inferencing using light alone

Researchers at UCLA have taken a trained DL neural network and implemented it into a series of passive optical only, 3D printed diffraction gratings to perform fashion MNIST object classification. And did the same with a MNIST handwritten digit and ImageNet DL neural network classifiers.

But first please take our new poll:

Experimental testing of 3D-printed D2NNs.(A and B) After the training phase, the final designs of five different layers (L1, L2, …, L5) of the handwritten digit classifier, fashion product classifier, and the imager D2NNs are shown. To the right of the network layers, an illustration of the corresponding 3D-printed D2NN is shown. (C and D) Schematic (C) and photo (D) of the experimental terahertz setup. An amplifier-multiplier chain was used to generate continuous-wave radiation at 0.4 THz, and a mixer-amplifier-multiplier chain was used for the detection at the output plane of the network. RF, radio frequency; f, frequency.

See the article on SlashGear, 3D printed all-optical diffractive deep learning neural network…. The research article is only available on Optical Society of America’s website/magazine (see Residual D2NN: training diffractive deep neural networks via learnable light shortcuts behind hard paywall). However, I did find a follow on article on ArchivX (see Analysis of Diffractive Optical Neural Networks and Their Integration with Electronic Neural Networks) that discussed how to integrate D2NN approaches with an electronic NN to create a hybrid inference engine. And another earlier Science article (see All-optical machine learning using diffractive deep neural networks) that was available which described earlier versions of D2NN technology for MNIST digit classification, fashion MNIST classification and ImageNet object classification.

How does it work

Apparently the researchers trained a normal (electronic based) deep learning neural network on the MNIST, Fashion MNIST and ImageNet and then converted the resultant trained NNs into a set of multiple diffraction grids. They did some computer simulation of the D2NN and once satisfied it worked and achieved decent accuracy, 3D printed the diffraction plates.

All-optical D2NN-based classifiers. These D2NN designs were based on spatially and temporally coherent illumination and linear optical materials/layers. (a) D2NN setup for the task of classification of handwritten digits (MNIST), where the input information is encoded in the amplitude channel of the input plane. (b) Final design of a 5-layer, phase-only classifier for handwritten digits. (c) Amplitude distribution at the input plane for a test sample (digit ‘0’). (d-e) Intensity patterns at the output plane for the input in (c); (d) is for MSE-based, and (e) is softmax- cross-entropy (SCE)-based designs. (f) D2NN setup for the task of classification of fashion products (Fashion-MNIST), where the input information is encoded in the phase channel of the input plane. (g) Same as (b), except for fashion product dataset. (h) Phase distribution at the input plane for a test sample. (i-j) Same as (d) and (e) for the input in (h),  refers to the illumination source wavelength. Input plane represents the plane of the input object or its data, which can also be generated by another optical imaging system or a lens, projecting an image of the object data onto this plane.

In their D2NN, they start with coherent (laser) light in the THz spectrum, used this to illuminate the input plane (I assume an image of the object/digit/fashion accessory) and passed this through multiple plates of diffraction grids onto THz detector which was used to detect the illuminated spot that indicated the classification.

The article in science has a supplementary materials download that show how the researchers converted NN weights into a diffraction grating. Essentially each pixel on the diffraction grating either transmits, refracts, or reflects a light path. And this represents the connections between layers. It’s unclear whether the 5 or 6 plates used in the D2NN correspond to the NN layers but it’s certainly possible.

And to the life of me I can’t understand what they mean by “Residual D2NN”, other than if it means using a trained (residual) NN and converting this to D2NN.

Some advantages of D2NN

3D printing diffraction gratings means anyone/lab could do this. The 3D printers they used had a spatial accuracy of 600 dpi, with 0.1mm accuracy, almost consumer grade 3D printers. In any case, being able to print these in a matter of hours, while not as easy as changing an all digital NN, seems like an easy way to try out the approach.

For example, for the MNIST digit classifier they used a pixel size of 400um and each diffraction layer they created was equivalent to 200X200 neural weights. Which means that 5 layer D2NN could handle about 0.2M neural weights which were completely connected to one another. This meant they could have (200×200)**2*5=8B connections in the MNIST D2NN. In the image classifier, each diffraction layer had 300×300 neural weights. So D2NN’s seem to scale very well.

Being an all passive optical device, the system is operates entirely in parallel, That is, the researchers indicated that the D2NN devices operate at the speed of light and would perform the inferencing activity in the time it takes a camera to capture the image.

Also the device uses very little energy (I assume just the energy for the THz generator, the input plane detector and the THz detector at the end.

And the researchers also claimed the device was cheap to manufacture, it could be created for less than $50. (Unclear if this included all the electronics or just the D2NN diffraction gratings and holder). And once you have locked into a D2NN that you wanted to use, could be manufactured in volume, very cheaply (sort of like stamping out CD platters). Finally, the number of neural network nodes and layers can be scaled up to a large number of layers and nodes per layer while still fitting on the diffraction gratings. In contrast, all electronic NN require more compute power as you scale up network layers and nodes per layer.

The other article (ArchivX) talked about potentially using a hybrid optical-electronic DNN approach with some layers being D2NN and others being purely digital (electronics). Such a system could potentially be used where some portion of the NN was more stable/more compute intensive than others and where the final output classification layer(s) was more changeable and much smaller/less compute intensive. Such a hybrid system could make use of the best of of the all optical D2NN to efficiently and quickly compress the input space and then have the electronic final classification layer provide the final classification step.

The Oracle

Combining a handful of D2NNs into a device that accepts speech input and provides speech output with the addition of say an offline copy of Wikipedia, Google Books etc. with a search engine that could be used to retrieve responses to questions asked would create an oracle device. Where you would ask a question and the device would respond with the best answer it could find (in it’s databases).

If this could be made out of an all passive optical components and use natural sunlight/electronic illumination to perform it’s functionality, such an all optical, question to answer oracle would be very useful to the populations of the world. And could be manufactured in volume very cheaply and would cost almost nothing to operate.

A couple of other tweaks, if we could collapse the multiple grating D2NNs into a single multi-layer plate/platter and make these replaceable in the device that would allow the oracle’s information base to be updated periodically.

Then if we could embed such a device into a Long Now Clock that would reflect sunlight onto the disk every Solstice, or Equinox, then we could have a quarterly oracle device that could last for 1000 of years. That would provide answers to queries one day every quarter. And that would be quite the oracle…

Photo credit(s):

Ok, maybe neuromorphic chips aren’t a deadend

Those of you who followe my blog will no doubt recall that I pronounced neuromorphic chips dead (see our Are neuromorphic chips a deadend blog post). Not because the hardware technology wasn’t improving or good enough, but because software support for the technology was sorely lacking and it was extremely complex or nigh impossible to program and use.

But first please take our new poll:

And, in the meantime GPUs, TPUs and other more “normal” neural network hardware and accelerators, all were able to utilize standard, easy to use, mostly open source, AI DL frameworks. And all this hardware was steadily improving, coming out regularly with more power and performance, with no end in sight.

But then I attended AIFD1 (AI Field Day 1) and at one of the sessions, Anil Mankar, COO & Co-Founder of a company named BrainChip Inc, (see video of their talk) presented yet another neuromorphic chip, called the AKIDA Neural Processor. Their current generation of the technology is available in their AKD 1000 SoC chip, focused on IoT solutions. But they had created a a software development environment that allowed one to use standard TensorFlow neural network trained models and deploy these on their hardware. And that got my interest.

BrainChip’s AKIDA AKD 1000 hardware AND software

Their AI DL nueromoryhic chip is made app of Event Domain Neural Processing Units (NPUs). AKIDA technology is focused on low power, sensor like applications. They claim to save power by only consumuing power (or is running) when an event takes place. They are also able to save on memory requirements by using 1, 2 or 4 bits (vs. 8, 16, 32 or more bits) for model weights/activations

Their hardware seems to run spiking neural networks (SNN, see our blog post on another chip technology using SNNs). In their SDK, they have a CNN2SNN tool that could take a any (TensorFlow) trained CNN model and convert it to a SNN, that could then run on their AKIDA tecnology.

They also have an AKIDA Model Zoo with a handful of pre-trained CNN type models that have already been converted to run on their technology. They also provide a tutorial on their technology. Mankar, said that if you understand how to use TensorFlow Keras today, to construct and train your models, it shouldn’t be too hard to understand how to use their tools to do what you want.

Their chip hardware is available today on a separate PCIe card, M.2 form factor card. or as a chip. Finally, they also license their AKIDA IP to other chip designers.

AKIDA AKD 1000 performance

At the AIFD1 Mankar showed statistics on the performance and accuracy attained using their chip vs. using standard 32 bit floating point CNN implementations.

As discussed above, their processor uses 1-4 bits for weight quantization and as such loses some accuracy but as you can see it’s a matter of one to a few percent vs. these same models using a 32bit floating point CNN implementation.

Because of their smaller weights, AKIDA uses less memory and less bandwidth to update models vs. models using larger weights.

As shown in the chart the the memory required for the 8-bit deep learning algorithms (DLAs) were all significantly larger than the memory requirements for the AKIDA solution. For one algorithm, they required ~1/2 the memory size of the 8-bit DLA version of the model.

Mankar also provided information on the amount of calculations required per inference using AKIDA vs. 8-bit DLAs.

Just to set the stage, MMACs/Inference is (matrix or multiple) multiplications and accumulations required to perform a single inference with the selected CNN model. ImageNet (1000), ImageNette (20) and Visual Wake Word models are all standard CNN models, that have pre-trained on vast repositories of data, that can run in many hardware environments. The non-AKIDA solutions above were all running using an 8-bit DLA CNN model. Activity regularization is a method of reducing the learning rate and weights used during training that shrinks the weight changes during training to reduce model overfit.

He also showed some comparisons of their technology vs. Intel’s LoiHi hardware. LoiHi is another neuromorphic chip, whose original introduction prompted me to write the “Are neuromorphic chips a deadend” post (link above). Unfortunately, I didn’t capture any of these charts, but from my recollection, they showed that AKIDA technology used slightly less power than LoiHi technology in all their comparisons.

AKIDA technology demo

In their live, on camera, demo, they used a previously downloaded VGG16 (if I recall correctly) CNN trained model. Offline they had replaced the last classification layer with a (blank, untrained) dense network and they converted this to a SNN and downloaded onto one of their boards. They had developed an application that used this board with a camera to perform more CNN training or CNN image inferencing (classification).

They first (one-shot) trained their board’s model to recognize the background of what the camera was seeing and then proceeded to perform (one-shot) trainings to classify toys of tigers, elephants and cars. All these were completed in real time in the demo. They were able to verify the training took using pictures of tigers, elephants and cars as well as classify all the toys in different orientations and a different toy car

The AIFD1 (a tuff) crowd, said had seen all this before but would be really interested to see if their chip could distinguish between different cars (one a toy race car and the other a toy police car). On camera, they were able to re-train their CNN to distinguish between (toy) car 1 and car 2 to classify properly between the two of them. They had one or two instances where their CNN model was confused, but they were able to re-train it to recognize the toy car and place it into the correct classification (using two-shot[?] learning).

At AIFD1, Mankar also presented detailed, real world data on how they were able to perform Keyword spotting, person detection, E-nose classification, E-tongue classification, and auditory (E-ear?) classification in embedded sensor systems.

AKIDA technology limitations

At the moment, their chip doesn’t support neural networks that use memory such as LSTM or RNN’s but it seems to work fine for any CNN, which was shown multiple times in the data they presented and in their demo.

We were really impressed with their software stack, liked what we saw of their hardware/IP, and enjoyed their demo and its one-shot learning. Check out their videos (link above) for more information on them.

Photo Credit(s): all charts are from BrainChip Inc’s website or were presented at their AIFD1 session