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Green software engineering

22 April, 2021 | 31 min 2 sec
Podcast Host Rebecca Parsons and Alexey Boas | Podcast Guest Isabelle Carter and Ken Mugrage
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Brief Summary

There’s increasing awareness of tech’s carbon footprint but to what extent can software developers help? Is it possible to measure the energy efficiency of your code? Can you write code that saves energy? Our podcast team unpick the art of the possible when it comes to green software engineering.

Podcast transcript


Rebecca Parsons:

Hello, everybody. Welcome to the ThoughtWorks technology podcast. My name is Rebecca Parsons, the CTO of ThoughtWorks, and I'm one of your regular co-hosts and I'm joined by my other co-host Alexey.


Alexey Boas:

Hello, everyone. I'm Alexey Villas Boas speaking from São Paulo. Very happy to be here.


Rebecca Parsons:

Great. And today we are joined by two guests. Isabelle Carter is a developer working with the office of the CTO on research projects. And Ken Mugrage is another member of our office of the CTO who has a long history in thinking about issues of dev ops and continuous delivery. So welcome, Isabelle and Ken.


Isabelle Carter:

Thank you.


Ken Mugrage:

Thank you.


Rebecca Parsons:

And today what we want to talk about is green or sustainable software engineering. And I want to start by contextualizing this a little bit because we aren't going to talk about all of the issues around green cloud. And we know that's a big part of how organizations are looking to achieve their sustainability goals, but we have a whole other podcast that's going to be focused on that. So what we want to talk about instead are things more at the software development level. So things around how we create our code, how we measure our code, how we test our code, things of that nature. So to start off first, what are the reasons that this is even an important topic? I mean is this just green washing?


Isabelle Carter:

I mean, I would say it's not really, even if we ignore the obvious answer of the environmental impact, there's definitely a business case to be made for trying to create more energy efficient software. Reducing the energy impact will save costs. Cost is the big one. You have reduced the cost of your data centers of the offices you're in, so that's a really easy benefit to see. Outside of that, there's also battery life, particularly for mobile devices, but outside of that as well, and things like sensors and autonomous devices, if you can increase the battery life of those, it'll also save money in the long run.


Rebecca Parsons:

Let's say I'm conscious of the energy consumption of the code that I write. What do I do? How do I get started? What kind of tools or frameworks or algorithms or whatever is out there to help me?


Isabelle Carter:

I would love to just pick up something and hold it up on a pedestal and say, look at this. We should all be using this, but unfortunately there's nothing like that quite yet. There are tools out there to measure the energy consumption of software, but nothing quite as developed as we would hope. There are two primary categories when it comes to measuring the energy output of software, there's physical device measurement, which is a physical device that you hook up to the power supply of the machine, and that will measure the total power consumption of the machine. And you can get the energy from that. And then there's software that'll do it as well. The software side is where it's going to be, in the future, easier to actually measure the energy consumption of software. The problem is, is it hasn't gone that far yet.


Isabelle Carter:

The area where it's best would be mobile devices around Android and iPhone. They have some pretty great interfaces that allow you to dig deeper than most other things and to find out where the energy is being consumed. Beyond that, when it comes to the server and desktop side, it's all kind of a mess. Most of it's from academic research, but there are a few tools like Power API, where you can, if you take the time to set it up, which would be a process, where you can get some good data out of it, it would be very raw data though. And it would be a lot of work to actually go through and set it up. And most of the tools are very specific to architectures as well. So measurement is a huge barrier into writing energy efficient software. And so going forward in the future, I'm hopeful that someone will build up upon these tools and it will become much easier to get that data from it.


Ken Mugrage:

Yeah. So this is also one of those areas where the continuous integration and continuous delivery comes in because the tools aren't out there today, that's very, very true. But even if we had a magical tool tomorrow, if somebody releases a thing that's going to make really accurate measurements and allow you to set a baseline and all the things that we'd want to do to really track improvement, just a simple matter of running those tools in a continuous way is going to consume quite a bit of energy. You know, so if I am trying to make my energy consumption better and I run my pipeline a hundred times over a week or so with different configurations to see what the outputs are and so forth, depending on the application and how many users it's going to have, or how scalable it is, or what have you, I may have consumed more energy just in baseline and making a small improvement, then I'll end up saving over the life of that release or that deployment. So it's a really challenging thing where measuring it could be a higher impact than running it.


Isabelle Carter:

You might even have to consider trying to measure that measurement going on in CD.


Alexey Boas:

That's quite interesting. It feels like when we look back at some of the history of computing, we have come from a world of limitations of resources, but now it feels like we got used to infinite computing cycle resources. So the computer's on, so it doesn't matter if it's computing or if it's not. And then this is exactly going the opposite direction that no, no, we have to pay attention to that. But apparently we got to used to just using up resources freely, and then not caring about that.


Isabelle Carter:

Well, speed's been the name of the game forever now, and now we're at the point where, as you said, we have pretty much all the speed that we could ever want. I mean, we still want more, but we've kind of forgotten this energy aspect.


Rebecca Parsons:

So what do we know about how to approach making our software more energy efficient? Have we learned anything, really, anything that we could extrapolate from?


Isabelle Carter:

There's a fair amount known about making energy efficient technology. Most of it would be around the hardware side and then there's the green cloud, but in our sliver and actually writing green software, there's less knowledge, but there is some, and some of it's highly specific. It gets down to the level where there's good empirical data on the performance of programming languages when it comes to both speed and energy efficiency. Some of it's fairly obvious like C, C++, and Rust are very fast and very energy efficient and things like Ruby and Python, not so much, they're on the lower end. A surprising point would be Java. Java is actually pretty much middle of the road for all the metrics and does a pretty good job. So if performance is a concern and energy efficiency is a concern, you can look at what programming language you're using and make a choice based on that and what your goals are and get a very easy when they're outside of that, you can look at design patterns, there's some benchmarking on the design patterns, in their energy efficiency, things like the decorator pattern are really energy inefficient and intensive, but things like flyweight are really energy efficient.


Isabelle Carter:

And then there are ways to mitigate that energy inefficiency from some of those design patterns, through compiler transformations and things. So there are some very specific things you can do, you just have to know about it. And that information is not really that easily accessible. Most of these examples I'm mentioning are from academic papers and vast majority of us don't take the time to read academic papers unless you're kind of an academic nerd like I am.


Isabelle Carter:

And so that knowledge gap and barrier is a real issue here. And figuring out how to inform developers about these things is going to be important going forward. To name some other examples would be like thread management, depending on the problem you're solving, the style of thread management you use is going to have an impact on your energy. AIML, the dataset, they're the larger, it is the more energy inefficient it's going to be. As far as unknowns go though, I think the biggest one that stands out to me would be the relationship between object oriented programming and energy efficiency. That relationship is unclear how it's not a straightforward issue because these things really depend on multiple factors. You know, the programming language you're using, the hardware you're using, all these different things come together to affect this.


Isabelle Carter:

But what is that relationship between the objects you're creating, how they're interacting in the energy efficiency or inefficiency? That's a question that I don't know the answer to because it's fairly unclear, especially given some of the data that's out there. Sometimes it looks like when I'm looking at the data from different papers, it looks like it doesn't have that much of an impact, but then there are things like the decorator pattern where it's creating a lot of these smaller objects to the backend that you don't even think about or see. And because of all that, it's making it highly energy inefficient. So there's something kind of fundamental there that isn't quite understood yet about why that's inefficient and what is the relationship there.


Rebecca Parsons:

Well, and as a compiler person from long ago, one of the things I found interesting about the research you uncovered around things like the decorator pattern is, because the way it's a structural issue with how the compiler normally treats your use of the decorator pattern, which results in the creation of these objects, that there is kind of a structural optimization that can be done so that you can cheerfully write the decorator pattern code, but you could envision an optimization, a compiler optimization that during the compilation phase, could do a transformation on that to something that is more energy efficient. I was actually rather surprised because C++ relative to languages like C and Rust can be much more complicated in terms of being able to do a good job of optimization. And I think the positioning of Java in that has a lot to do with the work that's been done on the Jit compiler over the years. And so you can see how you can get a general uplift from some of this underlying compiler optimization technology, which I think is a fascinating area to explore.


Isabelle Carter:

Yeah, I think you're absolutely right. And one of the things that stood out to me about the decorator pattern is, it really is mostly cosmetic and for the developers, and that has such a big impact on the performance and energy efficiency, it kind of makes me take a step back and think about the times of refactored code and made it to where it's more readable. What was the real impact of that refactoring? Did it make the code actually better by some objective metrics or did it just look pretty?


Alexey Boas:

And then you have some of what Ken was talking about as well. Right? So if the code is harder to maintain and you introduce a bug, then you are going to need more energy to fix the bug you’re going to run into inefficiencies because of the bug and all that. So when we take that broader systemic approach, it doesn't get very much more complicated as well.


Ken Mugrage:

Yeah. And frankly, just that whole development process, you know, one of the things that we talk about in a continuous delivery world is the fast feedback, the feedback loops of, I made a change, whether it's to try to gain more energy efficiency or not, whatever the change is, I've made a change and I want to get feedback as quickly as possible if that broke something in my application, that's really the whole point of continuous delivery. And so there's a tension there, like there is, I think a lot of times in technology between, I want the fastest feedback I can get, I want to be able to deliver things. I want to run all of the tests all of the time. I'm not particularly a fan of the patterns that some people apply where they've tried to take away to say this change I made will only affect this part of the code. So only run those tests. Quite often, that's just simply not the case. And so frankly, and there's no good answer for it. At least I don't have one, but we have to acknowledge that there's these tensions out there that we're wanting to do things to get faster feedback loops and to get continuous delivery and continuous deployment and others, and those have an impact. And we need to at least be aware of that.


Isabelle Carter:

I mean, you're absolutely right and what you're getting at gets to a larger issue of balance. There are a lot of different variables that need to be balanced here and throwing energy efficiency into the mix only complicates things because the impact when you optimize for energy efficiency is going to have unforeseen impacts on your performance. And then there's also as you're optimizing, as we've been talking about continuous deliveries, is as you optimize, you're going to be spinning energy. So are you going to end up in the red or are you going to end up in the black?


Ken Mugrage:

Yeah. And I mean, one of the things that I've seen that helps this for sure, maybe not on purpose, Rebecca likes to talk about second and third order effects. But when, if you have a small component architecture, whatever label you want to put on it, microservices, or what have you, the smaller the code base of the thing that you're changing, the lower the number of tests, the lower of things you're running and doing it, but of course there's the trade-off for complexity. And so it's just this interesting thing where your pipeline can be faster and you'll use less energy, and hopefully your changes are easier to track and test and those types of things, but you are getting your trading complexity for that. And so it's a balancing act.


Rebecca Parsons:

And it has to be balanced as well against, what is the cumulative energy cost of this thing running and production. Isabelle mentioned training of machine learning models. If you only train the model once a year, but you run that model, say as fraud detection for every credit card transaction that comes through, you would probably think about, well, let's worry about the energy efficiency of the model because it's running billions and billions of times. And I'll perhaps worry a bit less about the energy costs of the training run, because I'm only going to do that once a year. And so it is this grand trade-off of what am I looking at in production, and how does that relate to what's happening in the context of the software development life cycle, whether that be model training, whether that be our bills, et cetera. And so, and it's often very difficult, I mean that's a pretty blatantly obvious example. You know, if something's happening for every credit card transaction that happens, you know that's going to be running a lot, but it's perhaps not always quite as obvious where the bulk of energy consumption would come from. And therefore, where should I think about optimization?


Alexey Boas:

And Isabelle, you did mention one thing that I'm curious about that I know that you looked at that and it's in your research. So about energy efficiency being a new variable that adds to the complexity. So, I mean, my intuition would tell me that there's a strong correlation between energy efficiency and speed, but if I'm consuming less energy, I have fewer competing cycles, things run faster and it's not the same thing, right?


Isabelle Carter:

It's not, and it's pretty unintuitive. And it was surprising to me at first, but there is a direct relationship between time and energy. The formulas that commonly gets used involves both time and power. So there's definitely a strong connection there, but it's not straightforward. There's a lot of data out there that just shows that sometimes as you increase the performance or make it faster, you end up spending more energy. And sometimes the opposite happens as well. So we all want things to be fast and highly performant, but the cost of that in many cases is a highly energy inefficient code. And so is the opposite. So if you want to make something energy efficient, you also need to keep in mind and have this balancing act going on of, okay, well, it needs to be fast enough to actually meet our needs, but we don't want it to be energy inefficient.


Isabelle Carter:

So you might have to take a step back and make it slower to get some more energy efficiency and trying to balance that is difficult. One of the best examples I can think of where the energy efficiency and performance don't quite align, it's with thread management. In the data that's out there, in some cases, as you increase the amount of threads, you get higher performance, as you would expect, but the energy efficiency, you end up spinning much more energy, the more threads you throw into the mix. And so it really depends on the type of problem, and you have to keep this in mind and try to balance it. And that balancing act is very difficult. I don't know how to advise someone to do that yet. That's something that would come down to your requirements, having discussions, figuring out what your needs are. And there's not really a methodology out there that really talks about that.


Rebecca Parsons:

So it seems like we have lots of different trade-offs that we've kind of alluded to. I want to drill in a little bit more to the trade-offs of the software development life cycle. You mentioned speed of feedback and application complexity, any thoughts on how we even begin to try to model or make the trade off decisions of, is the delay of the feedback on the functionality, is that delay better or worse than what we're doing from an energy perspective and any thoughts really on how we might even go about thinking about this?


Ken Mugrage:

Well, that's actually a really tough question because I always want to say the fastest feedback possible. Every change runs the pipeline, every change runs every test, et cetera, because there are other efficiencies gained by that, being able to fix the smallest amount of code when something changed and when something breaks, et cetera, there's lots of gains by getting that faster feedback. But I think like a lot of things, you have to take a realistic view on it. So what I mean by that is, if I think I'm going to gain two or three minutes faster feedback, and yet I'm giving up, like the multi-threaded example is a great example, it's a little bit faster, but it's orders of magnitude more, well, could be more inefficient, then I have to be realistic about that.


Ken Mugrage:

You see a lot of times, especially when people are talking about continuous integration, even before the continuous delivery, oh, all my tests run in 23 seconds and woo hoo, you know, I mean, that's great, but first off, it's a signal to me that you're probably not really running all of the tests. You're probably not running. And by that, I mean all of the categories of tests. If you're really getting feedback that quickly, you're probably not running security compliance, et cetera. But maybe depending on the risk of your project, that's okay. You know, if you're at a large enterprise and you're creating the service that provides animated gifs to the chat server, maybe it's okay to only run the security stuff when you're a little bit farther to the right down the pipeline so that you can get the faster feedback and not be using that energy and that time upfront.


Ken Mugrage:

But if you're running credit card processing, especially if you're my bank, please do run the compliance and security tests in that first batch. So it's really about looking at it case by case. I think it's not something I've ever seen done, but I think having something like, you see risk mitigation plans. So if we're collecting this kind of data, these are the kinds of compliance checks we have to do, those types of things. You know, maybe it'd be good for organizations to come up with those guidelines. So we want self-organizing teams, at least teams could look at the guidelines and learn from that and know when to apply the different things because there's really no easy answer to it.


Rebecca Parsons:

So let's pursue that a little bit more. Do you think we're at the stage of maturity and understanding about the energy efficiency of code to be able to come up with some general principles or is that still too early?


Isabelle Carter:

Personally, I think it's probably still too early. There are some rules of thumb that I could quote off, but they're highly specific things. I think that for most people trying to write energy efficient software is probably not worth the investment at this point in time. For larger corporations, it makes sense. They have the time, they have the money, they have the personnel and the resources to invest in it. But at the moment it is a rather large investment to do. I mean, there are super easy things people can do, some of them I've mentioned already, like effective thread management, when your design patterns, effective caching, reducing the IO operations or doing them in bulk because they're highly energy inefficient. But beyond that, trying to get some principles and on the level of actually writing the software, that's very difficult, predominantly because, the thing that I always go back to in my head is, there's not a great way to get the data.


Isabelle Carter:

Like when you're doing performance optimization, the main thing you need is data. It's really hard to optimize performance if you don't know how fast it's going, same with energy, but it's a significant investment to get some of these tools up. And you might even have to rearchitecture in order to use some of the tools that are more effective, because they are very specific, some architectures. So it's a huge investment upfront, you're going to spend a lot of money on the energy to get that going as we've talked about. And then it gets hard because you may not be able to measure what you want to measure, pretty much the best you can get is per process level. And that's not going to tell you a whole lot about where you're spending that energy. So it's hard to give some of these guidelines, especially on a smaller case basis.


Ken Mugrage:

You alluded to something there that I think we often overlook, especially, I mean, the four of us on this podcast are technologists at core. And Isabelle, you mentioned upfront when we're talking about why even do this, that there is real business value here of, using less energy costs less money. There's also the business value of air quotes here that you can't see, doing the right thing. There's business value to that, frankly we see all the big, I know there's going to be a separate podcast on green cloud, but all the cloud providers touting their drive towards energy efficiency and so forth. Other enterprises can do that. Increasingly, research that we've done for like the ThoughtWorks Looking Glass, as people are making buying decisions based on the habits of organizations. So if you can demonstrate that you're putting effort into this area, people will choose you versus a competitor. So there are benefits to doing this that aren't measurable in the quantitative way that we as technologists want it to be. But I really do think there is a value to doing the right thing.


Isabelle Carter:

You're definitely right. I guess more of the level I was talking about is, are you getting that benefit if you try to apply it to the software you're writing? On a smaller scale basis, absolutely not, on a large scale basis, I think there is definitely a potential with the way things look right now, I'm hopeful in the future that things will continue to evolve and it will become much more straightforward and manageable to do energy optimization, just like performance optimization.


Rebecca Parsons:

So let's push on that question a little bit, if and when we get to this carbon neutral net zero future, will we still even care about this? Is this one of those things that, we're just in this time when climate change and sustainability have a huge focus?


Isabelle Carter:

The super cynical side of me says that the world's going to end so probably, it's not relevant, but I think it will, predominantly from the cost perspective.


Ken Mugrage:

You see, and I'm less sure, because let's say that we had the perfect renewable energy data center somewhere. So whether it be wind or solar or whatever it is, there are still real costs there, windmills break. They can require maintenance there, et cetera. And so even if we're not completely destroying the planet at the time, we're still doing things that require investment. These technologies aren't ever going to be cheap. I mean, they're going to be a lot cheaper, I hope, but there is still an investment there. You know, we have a hybrid car that was, I think, four or $5,000 more than the non hybrid version. You know, the technology is still a little bit more expensive and maybe we get there, but you still have to maintain those things and build those things.


Isabelle Carter:

Yeah. I think part of the way I hear the question is, if we don't have to care about the environment, do we care about energy efficiency? And I think yes, because I mean, as you were saying, it directly relates to cost and if you can make it more energy efficient, you're reducing the cost.


Rebecca Parsons:

Well, and I think in particular, when you start looking at more mobile devices, more remote sensors, those are just going to increase in numbers, not decrease. And each one of those, there's the cost associated with recharging it. And even if there isn't a climate impact or environmental impact, there is still the cost.


Isabelle Carter:

You're absolutely right. And that's in large part, the reason why the tools around measuring energy efficiency for software are pretty highly developed when it comes to mobile devices.


Ken Mugrage:

No, I think I just wanted to reiterate that I strongly believe there's a do the right thing factor here and the tools aren't there yet. And frankly, I don't have a lot of confidence that the tools will get there just because of the nature of the computing landscape. As we move more to edge computing for all kinds of reasons, less and less of the energy consumption is on my server, if you will. So I'm providing a service that the energy consumption is happening on a remote device, or at the edge, because I want to take advantage of low latency, things like 5G and Wi-Fi 6, et cetera. So I don't have a lot of confidence that the tools are going to get there, frankly, but I think we can make incremental improvements and that's better than doing nothing.


Isabelle Carter:

I'd say I, by and largely, agree. I hope the tools get there. I think the best shot that we have for the tools getting there is somebody picking up an open source project that's created out there, like power API, and helping that grow, or someone like Amazon creating a tool that they use internally and releasing that. I think that those are the two ways, but those are both long shots, but even if those tools don't get there, I think we can care about doing the right thing in terms of technology and put our efforts in the areas where it is more developed like green cloud and managing your servers, going with more environmentally friendly hosting services and things. I mean, there are things we can still do to make sure we're doing the right thing, even if we can't necessarily make our software more energy efficient right now.


Rebecca Parsons:

Well, Isabelle, Ken, thank you, Alexey. Thank you as well. I really enjoyed thinking about all of the different trade-offs, as we often say when we talk about so much about technology, it's always a balancing act. There are always trade offs and this, by introducing a new variable, we've introduced lots of different balance points that we need to consider. So thank you very much, Isabelle and Ken, and thank you all for listening to the ThoughtWorks technology podcast.

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