Welcome!

Wireless Authors: Elizabeth White, Srinivasan Sundara Rajan, Liz McMillan, Pat Romanski, Kevin Benedict

Related Topics: Java, XML, SOA & WOA

Java: 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
Things are being built upon cloud foundations to transform organizations. This CEO Power Panel at 15th Cloud Expo, moderated by Roger Strukhoff, Cloud Expo and @ThingsExpo conference chair, addressed the big issues involving these technologies and, more important, the results they will achieve. Rodney Rogers, chairman and CEO of Virtustream; Brendan O'Brien, co-founder of Aria Systems, Bart Copeland, president and CEO of ActiveState Software; Jim Cowie, chief scientist at Dyn; Dave Wagstaff, VP and chief architect at BSQUARE Corporation; Seth Proctor, CTO of NuoDB, Inc.; and Andris Gailitis, C...
SYS-CON Media announced that Cisco, a worldwide leader in IT that helps companies seize the opportunities of tomorrow, has launched a new ad campaign in Cloud Computing Journal. The ad campaign, a webcast titled 'Is Your Data Center Ready for the Application Economy?', focuses on the latest data center networking technologies, including SDN or ACI, and how customers are using SDN and ACI in their organizations to achieve business agility. The Cisco webcast is available on-demand.
Today’s enterprise is being driven by disruptive competitive and human capital requirements to provide enterprise application access through not only desktops, but also mobile devices. To retrofit existing programs across all these devices using traditional programming methods is very costly and time consuming – often prohibitively so. In his session at @ThingsExpo, Jesse Shiah, CEO, President, and Co-Founder of AgilePoint Inc., discussed how you can create applications that run on all mobile devices as well as laptops and desktops using a visual drag-and-drop application – and eForms-buildi...
The Industrial Internet revolution is now underway, enabled by connected machines and billions of devices that communicate and collaborate. The massive amounts of Big Data requiring real-time analysis is flooding legacy IT systems and giving way to cloud environments that can handle the unpredictable workloads. Yet many barriers remain until we can fully realize the opportunities and benefits from the convergence of machines and devices with Big Data and the cloud, including interoperability, data security and privacy.
IoT is still a vague buzzword for many people. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed the business value of IoT that goes far beyond the general public's perception that IoT is all about wearables and home consumer services. He also discussed how IoT is perceived by investors and how venture capitalist access this space. Other topics discussed were barriers to success, what is new, what is old, and what the future may hold. Mike Kavis is Vice President & Principal Cloud Architect at Cloud Technology Pa...
SYS-CON Events announced today that CodeFutures, a leading supplier of database performance tools, has been named a “Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9–11, 2015, at the Javits Center in New York, NY. CodeFutures is an independent software vendor focused on providing tools that deliver database performance tools that increase productivity during database development and increase database performance and scalability during production.
Dale Kim is the Director of Industry Solutions at MapR. His background includes a variety of technical and management roles at information technology companies. While his experience includes work with relational databases, much of his career pertains to non-relational data in the areas of search, content management, and NoSQL, and includes senior roles in technical marketing, sales engineering, and support engineering. Dale holds an MBA from Santa Clara University, and a BA in Computer Science from the University of California, Berkeley.
The Internet of Things (IoT) is rapidly in the process of breaking from its heretofore relatively obscure enterprise applications (such as plant floor control and supply chain management) and going mainstream into the consumer space. More and more creative folks are interconnecting everyday products such as household items, mobile devices, appliances and cars, and unleashing new and imaginative scenarios. We are seeing a lot of excitement around applications in home automation, personal fitness, and in-car entertainment and this excitement will bleed into other areas. On the commercial side, m...
The Internet of Things (IoT) promises to evolve the way the world does business; however, understanding how to apply it to your company can be a mystery. Most people struggle with understanding the potential business uses or tend to get caught up in the technology, resulting in solutions that fail to meet even minimum business goals. In his session at @ThingsExpo, Jesse Shiah, CEO / President / Co-Founder of AgilePoint Inc., showed what is needed to leverage the IoT to transform your business. He discussed opportunities and challenges ahead for the IoT from a market and technical point of vie...
The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
"People are a lot more knowledgeable about APIs now. There are two types of people who work with APIs - IT people who want to use APIs for something internal and the product managers who want to do something outside APIs for people to connect to them," explained Roberto Medrano, Executive Vice President at SOA Software, in this SYS-CON.tv interview at Cloud Expo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Performance is the intersection of power, agility, control, and choice. If you value performance, and more specifically consistent performance, you need to look beyond simple virtualized compute. Many factors need to be considered to create a truly performant environment. In his General Session at 15th Cloud Expo, Harold Hannon, Sr. Software Architect at SoftLayer, discussed how to take advantage of a multitude of compute options and platform features to make cloud the cornerstone of your online presence.
SYS-CON Media announced that Splunk, a provider of the leading software platform for real-time Operational Intelligence, has launched an ad campaign on Big Data Journal. Splunk software and cloud services enable organizations to search, monitor, analyze and visualize machine-generated big data coming from websites, applications, servers, networks, sensors and mobile devices. The ads focus on delivering ROI - how improved uptime delivered $6M in annual ROI, improving customer operations by mining large volumes of unstructured data, and how data tracking delivers uptime when it matters most.
In this Women in Technology Power Panel at 15th Cloud Expo, moderated by Anne Plese, Senior Consultant, Cloud Product Marketing at Verizon Enterprise, Esmeralda Swartz, CMO at MetraTech; Evelyn de Souza, Data Privacy and Compliance Strategy Leader at Cisco Systems; Seema Jethani, Director of Product Management at Basho Technologies; Victoria Livschitz, CEO of Qubell Inc.; Anne Hungate, Senior Director of Software Quality at DIRECTV, discussed what path they took to find their spot within the technology industry and how do they see opportunities for other women in their area of expertise.
DevOps Summit 2015 New York, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that it is now accepting Keynote Proposals. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long development cycles that produce software that is obsolete at launch. DevOps may be disruptive, but it is essential.
Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
"BSQUARE is in the business of selling software solutions for smart connected devices. It's obvious that IoT has moved from being a technology to being a fundamental part of business, and in the last 18 months people have said let's figure out how to do it and let's put some focus on it, " explained Dave Wagstaff, VP & Chief Architect, at BSQUARE Corporation, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Building low-cost wearable devices can enhance the quality of our lives. In his session at Internet of @ThingsExpo, Sai Yamanoor, Embedded Software Engineer at Altschool, provided an example of putting together a small keychain within a $50 budget that educates the user about the air quality in their surroundings. He also provided examples such as building a wearable device that provides transit or recreational information. He then reviewed the resources available to build wearable devices at home including open source hardware, the raw materials required and the options available to power s...
“The age of the Internet of Things is upon us,” stated Thomas Svensson, senior vice-president and general manager EMEA, ThingWorx, “and working with forward-thinking companies, such as Elisa, enables us to deploy our leading technology so that customers can profit from complete, end-to-end solutions.” ThingWorx, a PTC® (Nasdaq: PTC) business and Internet of Things (IoT) platform provider, announced on Monday that Elisa, Finnish provider of mobile and fixed broadband subscriptions, will deploy ThingWorx® platform technology to enable a new Elisa IoT service in Finland and Estonia.
Advanced Persistent Threats (APTs) are increasing at an unprecedented rate. The threat landscape of today is drastically different than just a few years ago. Attacks are much more organized and sophisticated. They are harder to detect and even harder to anticipate. In the foreseeable future it's going to get a whole lot harder. Everything you know today will change. Keeping up with this changing landscape is already a daunting task. Your organization needs to use the latest tools, methods and expertise to guard against those threats. But will that be enough? In the foreseeable future attacks w...