Welcome!

Mobile IoT Authors: Elizabeth White, Liz McMillan, Jeev Trika, Philippe Abdoulaye, Jayaram Krishnaswamy

Related Topics: Java IoT, Industrial IoT, Microservices Expo

Java IoT: Article

i-Technology Viewpoint: Laziness Sometimes Pays

The Gains Made by Better Algorithms Almost Always Outstrip the Gains From Better Hardware

Let me begin by a philosophical rant. There is a motto from scientific computing that carries to many areas of computer science:

/The gains made by better algorithms almost always outstrip the gains from better hardware./

I've frequently seen where algorithm improvements pay by factors of tens to tens of thousands in CPU time. One change I made in a numerical algorithm improved CPU requirements by a factor of 50,000: from weeks on a super-computer to minutes on a workstation.

Any business-savvy engineer knows that algorithm improvements come at a price: the engineer's time. Striking that balance makes software systems move forward rather than staggering to a halt in bloat and dysfunction. It also helps to use people who actually know what they are doing: knowing how to compile code doesn't make you a software engineer any more than knowing how to spell makes you a writer. End of rant.

On to (rant related) business. On most Web sites, think of how many times a data source will be used to retrieve the same data and produce the same content over and over again. Most successful services deliver a highly redundant amount of information to their users. For example, the JDJ website will deliver this (same) content to perhaps a hundred thousand users. If the servers are overtaxed, customers will experience significant delays or malfunctions.

There are several useful solutions to this. Well configured caching proxy servers come to mind, although server-side scripting make this difficult. Buying more hardware will eventually fix the problem, which may be the correct business solution.

But what about asking programmers to be a little more lazy?

For this article I've included the source for the LazyFileOutputStream. It acts just like a regular FileOutputStream except that, if created on a file that already exists, it /reads/ the data from the file instead of writes it. The stream compares what is already in the file with what you are currently writing to it. If at any point it sees there is a difference in the data you are writing this time compared to what is already there, the stream automatically switches to a write-mode that writes over the remainder of the file with the changes.

The upshot is, if your program generates the same output twice, the output file is unmodified the second time (leaving the original modification date). First, by simply changing FileOutputStream to LazyFileOutputStream, any downstream processing can use timestamp information on the files to check if they need to do anything at all. If the timestamp hasn't changed, then neither has the contents.

But wait, there's more! In addition to the standard close(), the LazyFileOutputStream also supports abort(). This method effectively states "I'm done now, leave the rest of the file alone." The remainder of the file will be the same, even without reproducing it. This means that, if you determine at an early point in the processing of the file that it's going to turn out the same, you can simply abort() to leave it alone. Its similar to the idea of not changing the modification dates on files which are rewritten with the same data, but allows for saving CPU time for the current process step as well as downstream processing..

Certain engines produce part of the template before you can conveniently intervene to decide if you really need to regenerate it. By opening up the output as a Lazy file, you can just abort() early and have the old version, with the the old modification time, around for downstream processing.

Okay, rant concluded and point made: CPUs around the planet are spinning through the same data tens of thousands of times producing the same content tens of thousands of times. Instead of buying great big servers to manage this, a smart caching policy based on lazy file writers and some modification time testing could save some sites that same wild-sounding factor of 50,000. Without having to buy 50,000 new servers.

Anecdote # 1. There is a certain technical advantage to this style of writing data as well: most storage devices are easier to read from than write to, adhering to the 80/20 rule: 80% of file access will be reads, 20% will be writes.. The LazyFileOutputStream takes advantage of that for the many files which are simply rewritten with the same content.

Anecdote # 2. There must be a few curled toes out there saying to themselves, "Why not LazyFileWriter?" There are good technical reasons for the OutputStream: the logic of the data written must be checked in its raw /byte/ format for the idea to work correctly, and you can always wrap this in an OutputStreamWriter, followed by a BufferedWriter, which is what I recommend.

Now I'm even done with the anecdotes. Have a nice day.

More Stories By Warren MacEvoy

Warren D. MacEvoy is Asst Professor of Comp Science in the department of Computer Science, Mathematics & Statistics at Mesa State College, Grand Junction, Colorado.

Comments (8) View Comments

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


Most Recent Comments
Bruce VanOrder 10/19/04 09:25:42 AM EDT

I remember the first PC I bought for myself ... A CompuAdd 286 with lots of memory - 2 MB RAM and a whopping 40Mb hard drive ! On this gargantuan drive I was able to put everytrhing I needed.... WordPerfect 5.1, TurboPascal 5.5, Lotus 123, dBaseIII+, etc, etc, and a few games .... AND I STILL HAD ROOM !

Now I have a Pentium with 256Mb RAM & a 20 Gb hard drive...
MS Office Professional, Borland Delphi, JBuilder, Oracle, SQL Server.

dBaseIII+ could fit on a 1.44Mb 3.5" floppy !

Those were the days my friend, we thought would never end ..
:-)

Warren MacEvoy 10/16/04 12:57:28 AM EDT

Response to Mark M.

Back in the bad-old-days designers would kick around which sort would be better to use. Now practically all sort problems are best solved with Collections.sort() or using a TreeSet or TreeMap. This is a total win situation: it's faster to write, easier to maintain, and better optimized than any roll-your-own sort. So there's almost no context: the Collections' sort is almost always better.

I'll claim LazyFileOutputStream sits one step lower than this: it's almost never worse, and sometimes better than a plain FileOutputStream. If you are writing small chunks to an unbuffered stream (or flushing() after every character), then the adapter pattern it uses to implement its magic may cost you a little in time (but negligibly compared to other costs related to this approach). There is also a buffer overhead because of the (IMHO silly) decision to leave fundamental memory operations like POSIX memcmp out of the java system libraries. But you're writing to a file, and well, that's just kinda slow.

But what you gain is information. When you're done .isDifferent() will tell you if there was a change without having to keep the old copy around to see if there was a change, and the timestamps will tell you even if downstream processing occurs in some logically distant place, like another process.

So there's very little to lose in almost any situation, and a great deal to gain if:

1. your template processing is file-based.
2. you generally only rebuild things unless
they are out of date with respect to their dependencies.

Without timestamp information, implementing part 2 may have seemed like a waste of time (which it would have been, since every template rebuild would look like it was different), but switching to LazyFileOutputStreams can make it effective.

Warren MacEvoy 10/15/04 07:07:48 PM EDT

My apologies, but somehow the wrong link was placed for the source file. The correct adddress to the LazyFileOutputStream which the article refers to is:

http://bpp.sourceforge.net/download/bpp-0.8.5b/src/bpp/LazyFileOutputStr...

JavaDoc'ed at:
http://bpp.sourceforge.net/download/bpp-0.8.5b/doc/javadoc/index.html

You might also note that the class uses abandon() instead of abort(), which is a minor change.

This has nothing to do with

http://www.jdocs.com/ant/1.6.2/api/org/apache/tools/ant/util/LazyFileOut...

Again, my apologies for any confusion this may have created...

Mark M 10/15/04 11:47:56 AM EDT

Response to Warren M.

The key question is not how much more complicated it is to write the class. The key question is what is the context of the problem? Too often generic solutions to problems are presented (even if that is not always the author's intention, these things can be easily mis-interpreted as such) and their validity/necessity almost always depends upon the context of the problem. You yourself emphasize the need for context in your response to Jim M. You have created a useful tool for yourself given the context of the problem you were trying to solve. When the next programmer comes along, the context may be completely different. Often times, many are lead to believe incorrectly in one size fits all philosophies, for instance, it is widely viewed within the industry by working folk like myself that the notions of Bertand Meyer and Kent Beck conflict when in fact they both may be valid solutions under differing contexts. Lack of context is the biggest complaint I have with books on process in this industry. Without it, many arguments are neither valid nor invalid, just ambiguous. There is at least one really bright fella who says a lot about context when he writes. His name is Fred Brooks.

Warren MacEvoy 10/14/04 10:42:09 PM EDT

Response to Mark M.

I agree that it usually a waste of time to optimize without profiling to know where your problems are. You must also have a business argument that the problem needs to be solved and that optimizations are the best way to solve it.

It is wrong to think that optimizations must be complicated. There's plenty of code out there that make poor or no use of Collections, which would be faster to write, maintain and execute if better choices were made. Good programmers should know how to use these features to improve turnaround, defects, and efficiency (the rant part of my article).

The purpose of the article is to point another kind of "low hanging fruit" related to file processing. After all, how much more complicated is it to write "LazyFileOutputStream" compared to "FileOutputStream"?

Response to Jim M.

Completely? Substantially. Completely claims they have nothing to learn from each other, yet there are many business problems with a short lifetime and plenty of rustic scientific codes are dutifully solving the problems they were designed to solve twenty and thirty years after they were written.

Again, the optimizations I'm suggesting don't need to be complicated. The LazyFileOutputStream is as simple as the code it replaces. How does that detriment readability or maintainability?

As far as longevity, I like the analogy of building a wall. The last row of the wall (business or scientific) can be very slipshod and the wall will still be a wall. Much software is written with the (sometimes correct) assumption that they will be part of the last row of bricks. But people change their minds, and what was once the last row is not anymore. In the real world, this is why tens of thousands of people die when there is an earthquake in a third-world country.

Should businesses be happy with a software design model analogous to the slums of Mexico City?

Response to Justin S.

Edit one line of an XML configuration file, changing one attribute. Many elements of your design depend on this XML file, but almost none of them depend on this one attribute. Your solution suggests detailed code to see if the attributes each dependency requires has changed, which would be hugely complicated to write and maintain.

Mine asks that you to rebuild the elements that directly depend on the configuration file. If they don't change, then you don't have to propagate updates further. Not a perfect optimization, but a much more practical one.

The LazyFileOutputStream supports your idea if you choose to pursue it. If a template decides it does not need to regenerate a target, it can simply abort() to leave the current contents alone without going to the trouble of regenerating all of it.

Justin Sadowski 10/14/04 08:27:34 PM EDT

While I agree with your thoughts about the value of avoiding writing the same data over and over, I have to disagree with your LazyFileOutputStream solution. If you find that you are writing the same data to the same file repeatedly, I would suggest that you improve this by avoiding the rewriting altogether, instead of just making the rewriting more efficient.

For example, perhaps you are writing the same output repeatedly because you are operating on the same input; i.e. the data in a database hasn't changed, or a source XML file hasn't changed. If you can detect your input hasn't been modified, you can avoid writing the output altogether.

I would like to hear more details about the specific situation(s) that you have used LazyFileOutputStream -- I would be interested to hear an example of a situation where my logic above does not apply.

Jim T. 10/14/04 07:09:02 PM EDT

Scientific computing and business computing are completely different. In the scientific communality you usually have a very small number of highly skilled people working on a program. That just isn't so in the business world. In the business world I care much more about readability and maintainability rather than speed for 99% of our code. In science, nobody will be using my programs 5 years from now, the data will have all been analyzed and the papers published, in business, the exact same code will be used 5 years from now (or at least it will be for the basis of the code). I believe this is true because it is true of my code from 5 years ago. The physics code is gone/useless and the business code is being resold every day.

mark mcconkey 10/14/04 05:51:12 PM EDT

Several years back I began reading Kent Beck's stuff (XP) and it struck a chord for me because many of my experiences were similar. I believe Kent's general notion is something to the effect that one should not optimize up front because its too difficult to predict the future, and the majority of the time you will have made your code unreadable for no reason whatsoever. Of course, any seasoned programmer has experienced enough to have a feel for when big troubles are over the hill and thus that some optimization up front will be needed. I think though, that what is missing in your article is a lack of discussion of context. If I have 3 weeks to finish something that will take 6 and 50 big whigs in a fortune 500 company have goals dependent upon the completion of my software, it doesn't matter how clever I am. It matters how fast I can produce what is needed. On the other hand, the creators of Amazon probably needed to be quite clever in order to deal with the magnitude of hits on their servers. Without context, its sort of useless to talk about optimization.

@ThingsExpo Stories
For basic one-to-one voice or video calling solutions, WebRTC has proven to be a very powerful technology. Although WebRTC’s core functionality is to provide secure, real-time p2p media streaming, leveraging native platform features and server-side components brings up new communication capabilities for web and native mobile applications, allowing for advanced multi-user use cases such as video broadcasting, conferencing, and media recording.
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, wh...
Ask someone to architect an Internet of Things (IoT) solution and you are guaranteed to see a reference to the cloud. This would lead you to believe that IoT requires the cloud to exist. However, there are many IoT use cases where the cloud is not feasible or desirable. In his session at @ThingsExpo, Dave McCarthy, Director of Products at Bsquare Corporation, will discuss the strategies that exist to extend intelligence directly to IoT devices and sensors, freeing them from the constraints of ...
Web Real-Time Communication APIs have quickly revolutionized what browsers are capable of. In addition to video and audio streams, we can now bi-directionally send arbitrary data over WebRTC's PeerConnection Data Channels. With the advent of Progressive Web Apps and new hardware APIs such as WebBluetooh and WebUSB, we can finally enable users to stitch together the Internet of Things directly from their browsers while communicating privately and securely in a decentralized way.
Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...
Technology vendors and analysts are eager to paint a rosy picture of how wonderful IoT is and why your deployment will be great with the use of their products and services. While it is easy to showcase successful IoT solutions, identifying IoT systems that missed the mark or failed can often provide more in the way of key lessons learned. In his session at @ThingsExpo, Peter Vanderminden, Principal Industry Analyst for IoT & Digital Supply Chain to Flatiron Strategies, will focus on how IoT de...
In his session at @ThingsExpo, Kausik Sridharabalan, founder and CTO of Pulzze Systems, Inc., will focus on key challenges in building an Internet of Things solution infrastructure. He will shed light on efficient ways of defining interactions within IoT solutions, leading to cost and time reduction. He will also introduce ways to handle data and how one can develop IoT solutions that are lean, flexible and configurable, thus making IoT infrastructure agile and scalable.
Complete Internet of Things (IoT) embedded device security is not just about the device but involves the entire product’s identity, data and control integrity, and services traversing the cloud. A device can no longer be looked at as an island; it is a part of a system. In fact, given the cross-domain interactions enabled by IoT it could be a part of many systems. Also, depending on where the device is deployed, for example, in the office building versus a factory floor or oil field, security ha...
An IoT product’s log files speak volumes about what’s happening with your products in the field, pinpointing current and potential issues, and enabling you to predict failures and save millions of dollars in inventory. But until recently, no one knew how to listen. In his session at @ThingsExpo, Dan Gettens, Chief Research Officer at OnProcess, will discuss recent research by Massachusetts Institute of Technology and OnProcess Technology, where MIT created a new, breakthrough analytics model f...
There are several IoTs: the Industrial Internet, Consumer Wearables, Wearables and Healthcare, Supply Chains, and the movement toward Smart Grids, Cities, Regions, and Nations. There are competing communications standards every step of the way, a bewildering array of sensors and devices, and an entire world of competing data analytics platforms. To some this appears to be chaos. In this power panel at @ThingsExpo, moderated by Conference Chair Roger Strukhoff, Bradley Holt, Developer Advocate a...
Fifty billion connected devices and still no winning protocols standards. HTTP, WebSockets, MQTT, and CoAP seem to be leading in the IoT protocol race at the moment but many more protocols are getting introduced on a regular basis. Each protocol has its pros and cons depending on the nature of the communications. Does there really need to be only one protocol to rule them all? Of course not. In his session at @ThingsExpo, Chris Matthieu, co-founder and CTO of Octoblu, walk you through how Oct...
SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, will compare the Jevons Paradox to modern-day enterprise IT, e...
There is little doubt that Big Data solutions will have an increasing role in the Enterprise IT mainstream over time. Big Data at Cloud Expo - to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA - has announced its Call for Papers is open. Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is...
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform and how we integrate our thinking to solve complicated problems. In his session at 19th Cloud Expo, Craig Sproule, CEO of Metavine, will demonstrate how to move beyond today's coding paradigm ...
IoT offers a value of almost $4 trillion to the manufacturing industry through platforms that can improve margins, optimize operations & drive high performance work teams. By using IoT technologies as a foundation, manufacturing customers are integrating worker safety with manufacturing systems, driving deep collaboration and utilizing analytics to exponentially increased per-unit margins. However, as Benoit Lheureux, the VP for Research at Gartner points out, “IoT project implementers often ...
So, you bought into the current machine learning craze and went on to collect millions/billions of records from this promising new data source. Now, what do you do with them? Too often, the abundance of data quickly turns into an abundance of problems. How do you extract that "magic essence" from your data without falling into the common pitfalls? In her session at @ThingsExpo, Natalia Ponomareva, Software Engineer at Google, provided tips on how to be successful in large scale machine learning...
SYS-CON Events announced today that Roundee / LinearHub will exhibit at the WebRTC Summit at @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LinearHub provides Roundee Service, a smart platform for enterprise video conferencing with enhanced features such as automatic recording and transcription service. Slack users can integrate Roundee to their team via Slack’s App Directory, and '/roundee' command lets your video conference ...
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
Digital transformation is too big and important for our future success to not understand the rules that apply to it. The first three rules for winning in this age of hyper-digital transformation are: Advantages in speed, analytics and operational tempos must be captured by implementing an optimized information logistics system (OILS) Real-time operational tempos (IT, people and business processes) must be achieved Businesses that can "analyze data and act and with speed" will dominate those t...