Tag Archives: Forrest H Bennett III

To be or not to be the memristor?

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The memristor (aka, memresistor), for anyone not familiar with it, is a contested ‘new’ circuit element. In my April 5, 2010 posting I gave a brief overview of the history as I understood it (the memristor was a new addition to the traditional circuit elements [the capacitor, the resistor, and the inductor]) and in my April 7, 2010 posting I conducted an interview with Forrest H Bennett III who presented an alternative view to the memristor as ‘new’ circuit element discussion.

Discussion has continued on and off since then but in the last few weeks it has become more topical with the publication of a paper (Memresistors and non-memristive zero-crossing hysteresis curves) by Blaise Mouttet at arXiv.org on Jan. 12, 2012.

I don’t feel competent to summarize the gist of Blaise’s paper so I’m excerpting a passage *from* Peter Clarke’s Jan. 18, 2012 article for EE (Electronic Engineering) Times,

Blaise Mouttet argues that the interpretation of the memristor as a fourth fundamental circuit element – after the resistor, capacitor and inductor – was incorrect and that the memory device under development at HP Labs is not actually a memristor but part of a broader class of variable resistance systems.

…

Since publishing his arXiv paper Mouttet has also been in discussion with an e-mailing list of researchers into non-volatile memory device physics.

Some e-mail correspondents have come out in favor of Mouttet’s position stating that trying to define any two-terminal device in which the resistance can be altered by the current passed through the device as a memristor, adds nothing to the understanding of a complex field in which there are many types of device.

The article and the comments that follow (quite interesting and technical) are worth reviewing if this area of nanoelectronics interests you.

HP Labs has responded to Blaise’s paper and subsequent debate, and before included an excerpt from the response, I want to include a few passages from Blaise’s paper,

The “memristor” was originally proposed in 1971by Leon Chua as a missing fourth fundamental circuit element linking magnetic flux and electric charge. In 2008 a group of scientists from HP led by Stan Williams claimed to have discovered this missing memristor . It is my position that HP’s “memristor” claim lacks any scientific merit. My position is not that the HP researchers have presented an incorrect model of a memristor or even an incorrect model of resistance memory. If this were the case it would not be so bad because an incorrect model could at least be proven incorrect and possibly corrected to produce a better model. My position is that the HP researchers have avoided presenting any scientifically testable model at all by hiding behind the reputation of Leon Chua and the mythology of the memristor. They have thus attempted to bypass the principle of the scientific method.

If the HP researchers had developed a realistic model for resistive memory (whether it is called “memristor” or by some other name) it could be vetted by other researchers, compared to experimental data, and determined to be true or false. If necessary the model could be modified or corrected and an improved version of the model could be produced.

This is not what has happened. (p. 1 PDF)

Here’s my excerpt of HP’s response (from Peter Clarke’s Jan. 20, 2012 article for EE Times),

The spokesperson said in email: “HP is proud of the research it has undertaken into memristor technology and the recognition this has received in the scientific community. In a little over three years, our papers, which were subject to rigorous peer review before being published in leading scientific journals, have been cited more than 1,000 times by other researchers in the field. We continue this research and collaboration with the electronics industry to bring this important technology to market.”

Deciding what something is and how fits into our understanding of how the world operates, in this case, a new circuit element, or not, has consequences beyond the actual discussion. If science is the process of posing questions, we need to test the assumptions we make (in this case, whether or not the memristor is a fourth circuit element or part of a larger system of variable resistance systems) as they can define the questions we’ll ask in the future.

As I noted earlier, I’m not competent to draw any conclusions as to which party may have the right approach but I am glad to see the discussion taking place.

*’from’ added on Sept. 27, 2016.

Foresight Institute’s 25th anniversary conference and celebration

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The Foresight Institute’s 2011 annual conference (Foresight@Google: 25th Anniversary Conference and Celebration) this weekend (June 24-26, 2011) is their 25th anniversary. They are planning to webcast the Saturday (June 25, 2011) and Sunday (June 26, 2011) sessions. As the conference is  held in Silicon Valley, California the sessions are on the Pacific Timezone. Here’s a look at the Saturday sessions (from the event schedule page),

9:00-9:15am   “Nanotech: the Next 25 Years” Christine Peterson, President/CoFounder of Foresight

9:15-9:45am   “Commercializing Nanotechnology”
KEYNOTE: James R. Von Ehr, II, President/Founder of Zyvex Labs

9:45-10:15am   “New Synthetic Methods for Development of Nanoscale Materials”
Matthew Francis, PhD, Rising star of nanotech at UC-Berkeley

Happy 25th anniversary to the Foresight Insitute@ Google conference!

Memristor update

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HP Labs is making memristor news again. From a news item on physorg.ocm,

HP is partnering with Korean memory chip maker Hynix Semiconductor Inc. to make chips that contain memristors. Memristors are a newly discovered building block of electrical circuits.

HP built one in 2008 that confirmed what scientists had suspected for nearly 40 years but hadn’t been able to prove: that circuits have a weird, natural ability to remember things even when they’re turned off.

I don’t remember the story quite that way, i.e.,  “confirmed what scientists had suspected for nearly 40 years” as I recall the theory that R. Stanley William (the HP Labs team leader) cites  is from Dr. Leon Chua circa 1971 and was almost forgotten. (Unbeknownst to Dr. Chua, there was a previous theorist in the 1960s who posited a similar notion which he called a memistor. See Memistors, Memristors, and the Rise of Strong Artificial Intelligence, an article by Blaise Mouttet, for a more complete history. ETA: There’s additional material from Blaise at http://www.neurdon.com/)

There’s more about HP Labs and its new partner at BBC News in an article by Jason Palmer,

Electronics giant HP has joined the world’s second-largest memory chip maker Hynix to manufacture a novel member of the electronics family.

The deal will see “memristors” – first demonstrated by HP in 2006 [I believe it was 2008] – mass produced for the first time.

Memristors promise significantly greater memory storage requiring less energy and space, and may eventually also be employed in processors.

HP says the first memristors should be widely available in about three years.

If you follow the link to the story, there’s also a brief BBC video interview with Stanley Williams.

My first 2010 story on the memristor is here and later, there’s an interview I had with Forrest H Bennet III who argues that the memristor is not a fourth element (in addition to the capacitor, resistor, and inductor) but is in fact part of an infinite table of circuit elements.

ETA: I have some additional information from the news release on the HP Labs website,

HP today announced that it has entered into a joint development agreement with Hynix Semiconductor Inc., a world leader in the manufacture of computer memory, to bring memristor technology to market.

Memristors represent a fourth basic passive circuit element. They existed only in theory until 2006 – when researchers in HP Labs’ Information and Quantum Systems Laboratory (IQSL) first intentionally demonstrated their existence.

Memory chips created with memristor technology have the potential to run considerably faster and use much less energy than Flash memory technologies, says Dr. Stanley Williams, HP Senior Fellow and IQSL founding Director.

“We believe that the memristor is a universal memory that over time could replace Flash, DRAM, and even hard drives,” he says.

Uniting HP’s world-class research and IP with a first-rate memory manufacturer will allow high-quality, memristor-based memory to be developed quickly and on a mass scale, Williams adds.

Also, the video interview with Dr. Williams is on youtube and is not a BBC video as I believed. So here’s the interview,

Memristors and nuances in a classification tug-of-war; NRC of Canada insights; rapping scientists

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Interestingly, there’s an item posted with today’s (April 8, 2010) date on the Nanowerk website from HP Labs reiterating the ‘memristor as a fourth circuit element’ concept that Forrest H Bennett has convincingly argued against first in his comments to my original posting (April 5, 2010) and, at greater length, in yesterday’s (April 7, 2010) interview.

Oddly, the item on Nanowerk, which I’m assuming is a news release from HP Labs as no author is listed, mostly regurgitates the HP Labs work on the memristor.

HP Labs researchers have discovered that the “memristor“ – a resistor with memory that represents the fourth basic circuit element in electrical engineering – has more capabilities than was previously thought. In addition to being useful in storage devices, the memristor can perform logic, enabling computation to one day be performed in chips where data is stored, rather than on a specialized central processing unit.

In fact, much of what’s mentioned in the news release and in the accompanying video was discussed in 2008 when they first published their work. The new excitement has been generated by a team at the University of Michigan (see April 5, 2010 posting), led by Dr. Wei Lu, who’ve proved that synapses in biological organisms behave like memristors. This means that the speculations that the HP Lab folks made in 2008 about hardware that learns are more likely.

As for the ‘fourth circuit element’ mentioned in the item, this brings me to classification schemes. These sorts of discussions can seem picayune to people who are not directly involved but classification schemes have a huge impact on how we think about the world around us and the ways in which we interact with it. For example, we think of the tomato and treat it as if it’s a vegetable when in fact, it’s a fruit. When was the last time you had some tomatoes and ice cream?

Whether the memristor is thought of as a ‘fourth circuit element’ (as per HP Labs and Dr. Leon Chua [as of 2003]) or a member of an ‘infinite periodic table of circuit elements’ (as per Forrest H Bennett) will have an impact on how memristors and other as yet unknown elements are investigated and understood.

As someone who doesn’t understand the particulars especially well, I find Forrest’s approach the more flexible one and therefore preferable. Classification schemes or models that are rigid both buckle as new information is added and tend to constrain it. For example, the Dewey decimal classification scheme used in most public libraries has been buckling under the pressure of adding new categories since the 1950s, at least. It’s the reason most academic libraries use the more flexible Library of Congress classification scheme, although that scheme has its problems too.

One final note, it seems that HP Labs is supporting the notion of a ‘fourth circuit element’ being added to the previous three (capacitors, inductors, and resistors) and they have the resources to distribute their preferred notion far and wide and repeatedly. Or as Forrest put it in one of his comments, “This “4th circuit element” business is marketing spin from HP …”

National Research Council of Canada Insights

In the wake of John McDougall’s appointment as the new president of the Canada’s National Research Council (NRC), Rob Annan over at the Don’t Leave Canada Behind blog has written a very important (if Canadian science policy interests you) piece about NRC.  Rob traces the organization from its beginnings.  From the posting,

The NRC was founded more than 90 years ago to advise the government on matters related to science and technology. It evolved into a federal research laboratory with the construction of the Sussex Dr. labs in the 1930s, and was the focus of Canada’s research efforts during WWII. Post-war, the NRC expanded and was a major source of Canadian research success, with notable achievements like the invention of the pacemaker, development of Canola and the crash position indicator.

From the 1950s through the 1970s, NRC’s success, growth, and increasing complexity led to the creation of spin-off organizations. Atomic research went to the Atomic Energy of Canada, defense research went to the Defense Research Board. Medical research funding went to the Medical Research Council, later the CIHR. Lastly, support for academic research was passed to NSERC.

All of these organizations have grown and prospered. The NRC? Not so much.

He goes on to trace developments to the present day,

The NRC has research institutes in every province in the country, from the Herzberg Institute of Astrophysics in BC to the Institute for Ocean Technology in Newfoundland. A total of 26 institutes across the country, covering all aspects of science and technology, and employing more than 4,000 people. It’s a broad effort and employs a lot of great scientists.

But since the 1980s, the NRC has been without a strong sense of self. Is it a basic research organization or an applied research organization? Does it exist to perform independent, government-sponsored research, or does it provide research services in support of the private sector? Does it perform early-stage research and then partner with industry, or is it a fee-for-service research organization? The answer is yes.

I encourage you to read his posting as there’s more to his history and analysis and he goes on to make some suggestions. Please don’t forget to read the comments which offer additional insights.

Dave Bruggeman (at Pasco Phronesis) also mentions Rob’s NRC posting in the context of explaining that the current US National Research Council differs greatly from the Canadian one and warns against assuming that organizations with similar names are the same. You can go read Dave’s description of the US NRC here. This is a timely reminder as the ‘reinventing technology assessment’ webcast that the Project on Emerging Nanotechnologies is hosting later this month features a speaker from the US National Research Council.

Rapping biologists and physicists

While browsing on Dave’s (Pasco Phronesis) blog, I found an item that features two videos of scientists rapping. The first comes from some physicists and the second comes from biologists. I agree with Dave that the biologists have the edge since they rap in front of a live audience although both videos are quite entertaining.

Interview about memristors with Forrest H Bennett III

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In response to my posting about memristors the other day, Forrest Bennett made intriguing comments which I followed up with some questions that he has kindly taken the time to answer. I usually split the interviews over a few days but this time I think it’s best that the interview remain in one piece. First a few biographical details, then the Q & A. [Square brackets indicate a detail that I’ve added for clarification.]

Forrest H Bennett III is a senior research scientist at Genetic Programming, Inc. He has published 55 papers and a book, “Genetic Programming III: Darwinian Invention and Problem Solving”. He holds 7 patents in machine learning, automatic programming, analog circuit design, molecular mechanics, modular robotics, programmable smart membranes, reconfigurable hardware, and control systems.

Q & A

> 1.. Could you expand your comment [in response to my blog posting of April 5, 2010] that memristors have potential by indicating what those are?

The main potential of memristors is to replace current flash memory devices. Flash memory is used in almost all digital products: cell phones, cameras, camcorders, USB memory sticks, music players, ebooks, PDAs, and increasingly netbooks, notebooks, tablets, and servers. Flash memory is currently a $20 billion market and growing. Flash memory storage is preferred over hard disks because it is smaller, faster, lower powered, and inherently more reliable because it has no moving parts.

So there is a large and growing demand for inexpensive higher capacity flash memory. This requires chip makers to shrink these flash memory chips ever smaller and smaller. The problem is that this is getting quite challenging, and will become more so in the next few years.

Memristors could meet this demand for low-cost high-density memory. Memristors are inherently simple, small, fast, and low powered. Moreover, engineers at HP claim that they can construct memristor memories in 3D instead of just the 2D of current flash technology. Memristors are not exotic to manufacture, and hence could be quite inexpensive. In fact, current memristors are produced using standard chip production facilities, but not yet in sufficient quantities for productization.

There is also a lot of discussion recently about using memristors to build “neuromorphic” systems. Neuromorphic systems are supposed to work analogously to the way brains work. Memristors could be used to build neuromorphic systems that are smaller, faster, and cheaper than could be built using conventional digital technology. The reason that memristors are considered for this task is that mathematically they behave similarly to the synapses in neurons.

> 2.. Is the criterion (or one of them) for defining a new fourth element circuit that someone assigns a unique measurement for the element?

There isn’t really a rigorous way to define what a new circuit element would have to look like. But there are three arguments against the idea that a memristor is a 4th circuit element:

First, the weakest argument is that memristance is measured in the same units (ohms) as resistors, whereas the standard 3 circuit elements each have their own units of measure. This is a very simple and intuitive way to think about it, but it’s not a rigorous argument.

Second, a stronger argument is based on what we now know about memcapacitors and meminductors. Now you might be temped to regard memcapacitors and meminductors as the 5th and 6th new fundamental circuit elements, but nobody does. Why?

If you stand back and look at the actual behavior of these 6 circuit elements, it is very clear that they naturally fall into two groups. One group is the normal resistor, capacitor, and inductor. The other group contains the new memresistor, memcapacitor, and meminductor. There is no way to consider the memristor to be the 4th element of the first group. The unmistakable distinction between these two groups is that the first group are “linear” elements, and the second group are “nonlinear” elements. What does that mean?

In a linear element there is a very simple relationship between the inputs and the outputs. So if you double the input, it doubles the output. If you cut the input in half, it cuts the output in half.

But in a nonlinear element the relationship between the input and the output can be much more complex. In fact, nonlinear elements can have arbitrarily complex relationships between inputs and outputs.

The third and strongest argument against the 4th element idea actually comes from Chua’s own 2003 paper, “Nonlinear Circuit Foundations for Nanodevices”, which is a wonderful paper. It actually contains an idea even more exciting than the idea of a “4th element”. He shows an entire periodic table of circuit elements! Not only that, it’s an infinite periodic table of circuit elements! If you think he might just be pulling elements out of a hat, I must point out that he proves in this paper that all of these circuit elements are *required* if you want to be able to build all possible circuits.

Now if you look at this periodic table of circuit elements, you will see that they fall naturally into 4 classes. There is one class that contains both capacitors and memcapacitors, another class that contains inductors and meminductors, and another class that contains *both* resistors and memristors. That is the strongest argument against the “4th element” idea: Chua’s own paper puts resistors and memristors into the *same* class of elements.

You may have noticed that I mentioned only 3 of the 4 classes in the periodic table. That’s right, there *is* a 4th class of devices that you’ve never heard discussed, but it’s not memristors!

> Does Chua still theorize that the memristor is a fourth circuit element?

Yes, he is still sticking by that as of 2003 at least. If you want to call memristors the 4th, memcapacitors the 5th, meminductors the 6th, then you are forced keep going through the entire periodic table and talk about the 7th, 8th, and so on up to infinity. That’s fine. However, you can not say that a memristor is as different from a resistor as a capacitor is from an inductor – that’s not true. And you can see that it’s not true by looking at Chua’s own periodic table.

> 3.. In mentioning the memcapacitors and meminductors along with memristors, you suggest that all of them are non-linear “generalizations” and more accurately viewed as subsets rather than new categories. Could you explain the concept of a non-linear generalization in language that could be understood by a non-technical audience?

(See above explanation of linear vs nonlinear.)

Since a linear element is a very restricted special case, and a nonlinear element can be arbitrarily complex, that means that linear elements are subsets of nonlinear elements. Which means that nonlinear elements are generalizations of linear elements. (I think you said it backwards.) [Yes, I did.]

> 4.. Are there any analogies or metaphors that you could suggest that a writer (such as myself) could use when trying to explain memristors and such to a non-technical audience?

Electrical current is analogous to water flowing in a pipe. The diameter of the pipe acts like a resistor. If you make the pipe smaller, there is more resistance to the water flow. Similarly, if you make the electrical resistance larger, there is more resistance to electric current flow.

In our water example, the memristor is much like a pipe in that its size controls the resistance to the water flow. And both resistance and memristance are measured in ohms.

The difference with a memristor is that the more water that flows through the pipe, the bigger the pipe gets – so the resistance goes down. Then if you run the water through the memristor in the opposite direction, the pipe gets smaller and smaller, and the resistance goes up. So with a memristor, you can control how big the pipe is by which way you run the water through it, and by how long you run the water through it.

> 5. Is there anything you’d like to add?

So why are memristors useful? Sticking with our water analogy, I can make the pipe bigger or small depending on which way I run the water through it. And, when I turn off the water, the pipe stays at whatever size it’s at. So the pipe has a memory. This means that I can use it to store data. I can run water through it in one direction to make the pipe big, and treat the big pipe like a stored digital ONE. Or can run water through it in the other direction to make the pipe small, and treat the small pipe like stored digital ZERO. Presto! We have a digital storage device. It may not sound very exciting when described like this, but the excitement is about just how small, low powered, simple, and 3D these devices can be.

But memristors can store more than just ONEs and ZEROs. They can also store intermediate values between ONE and ZERO depending on how long and hard I push the water through the memristor. This is what makes a memristor useful in simulating a neural synapse.

Thank you Forrest for your memristor insights.