Software Effort Estimation Considered Harmful

http://mattrogish.com/blog/2012/08/16/software-effort-estimation-considered-harmful/

by MattRogish • 14 years ago

122 78 14 years ago

gpcz• 14 years ago

I'm fascinated to know the author's opinion about Joel Spolsky's "Evidence-Based Scheduling" approach. The author mentions that breaking the schedule into the smallest possible pieces can lead to "overfitting," but Evidence-Based Scheduling uses previous programmer estimates vs. actual time to give a probabilistic schedule that changes with new events. Instead of a rigid ship date, Joel's method can give you a probability of shipping on a given date with the current information. Is Evidence-Based Scheduling still harmful, or is it basically the equivalent of the relative points-based estimation the author brought up at the end of the article?

jacques_chester7• 14 years ago

EBS looks to me like an elaboration of the old-school PERT 3-point estimation technique. By the Laws of Agile, everything invented before 2001 is busted and useless, so I guess EBS would go out with the bathwater for being tainted by association.

abhimishra• 14 years ago

A good read, and more-or-less in line with my observations from working at a couple big software companies. I think there is generally less value in estimating versus doing, especially for tasks/projects that are inevitable.

logn• 14 years ago

I think estimation can mostly be forgotten. The planning part which the author identifies is always helpful. Sure, get the team together to plan features and get a feel for the goals. Even get biz analysts together with folks to determine req's.

But do we really have to tell you how long it will take? When a lot of managers just take the estimate and multiply by three can these estimates really be trusted? What's the end game? Is it any different than just building it out? If you have a hard set of features then it will get done when it gets done. Just predict what half of what year. If you're an agile enterprise, then timebox the release and build out from there. Why must we all do this absurd dance of time estimating?

sliverstorm2• 14 years ago

The goal is be able to effectively load-balance and prioritize. If something won't take long, for example, it can be deferred (if needed) if it depends on something else that will.

Additionally, depending on the market and how important schedule is, it lets you know if the project will be hopelessly late and as a result whether it should be canned.

mattvanhorn• 14 years ago

Any project whose only value comes from being there first is a loser and should be canned before the estimating. "Hey Sergei, Larry says Alta Vista is on track to beat us to market, so lets scrap this search thing and invest in new DRM schemes"

thisisnotmyname• 14 years ago

There is a great deal of philosophy here, but I'd prefer to see some data that backs up his point. Can you show me a project in which investing in an estimate harmed it?

MattRogish5• 14 years ago

Peopleware, DeMarco and Lister, pg 27-29, alluded to in the post.

Namely: "The most surprising part of the 1985 Jeffery-Lawrence study appeared at the very end, when they investigated the productivity of 24 projects for which no estimates were prepared at all. These projects far outperformed all the others..."

Study refers to Jeffery and Lawrence, 1985 study, to which I cannot find the raw data, unfortunately.

MattRogish5• 14 years ago

I found the study:

http://www.sciencedirect.com/science/article/pii/01641212859...

Jeffrey, D.R. and M.J. Lawrence, "Managing Programming Productivity", The Journal of Systems and Software 5, (1985), 49-58.

tmurray• 14 years ago

First, continuous deployment works fine for web projects, but it's not an option if you've got a packaged product that you have to ship at some point. Agile is not a panacea for these environments.

It's important to differentiate between the two kinds of software that you can write. This is post is dead-on for developing truly new software (new features, stuff that fundamentally hasn't existed before, etc). However, estimation (even the kind of project-manager-driven estimation that most engineers, myself included, generally hate) can work really well for software where you're doing basically the same thing you've already done in the past such that the risk of unknown unknowns is extremely low. I've seen it in practice, and when you have a checklist of stuff to do that you've already done with very minor changes in the past that can't be automated for whatever reason (e.g., support a new piece of hardware, except that the new piece of hardware is basically the same as the old piece of hardware with very minor well-documented changes), you can estimate with surprisingly good accuracy.

pnathan• 14 years ago

Yes, but a decent amount of software is doing things that are relatively unique to the time, place, and organization creating it.

For those sorts of projects, you might as well use this equation for time to completion: sum of(number of lines in the spec/request * d4)*3 = days to complete.

arohner2• 14 years ago

> continuous deployment works fine for web projects, but it's not an option if you've got a packaged product that you have to ship at some point. Agile is not a panacea for these environments.

I think that misses one of the key insights of continuous deployment. The biggest gain in CD is not about actually pushing code to production on every commit, but working as you actually do push to production on every commit.

This means that commits are small, contain tests, are delivered frequently and don't break the build. That workflow is a good idea, regardless of the final product or industry.

I practice CD (hell, I built a company to do CD), but if I ever had to go back to shipping desktop software or whatever, I'd still practice CD.

jasonhanley2• 14 years ago

What is this "packaged" software you speak of?

btilly4• 14 years ago

He's sometimes right. There are lots of good reasons why you might need software schedule estimation. When you do, there is no point in throwing up your hands and saying, "You can't do that, everybody knows it." Instead get http://www.amazon.com/Software-Estimation-Demystifying-Pract... and teach yourself how to do it.

Why would software estimation matter? For many companies it matters a lot if you can announce something in time for Christmas. Or you might have to hit a deadline for compliance with a legal contract. Or you may be trying to prioritize two different possible products - without a sense of the effort involved you're lacking one of the parameters you need for such an estimation.

That doesn't mean that you always estimate. If the value proposition is clear enough, you're going to work on it until you're done and then you will be very happy. But the real world does not usually work like that.

MattRogish5• 14 years ago

"For many companies it matters a lot if you can announce something in time for Christmas."

It will be done by xmas or it won't. I don't recommend "no estimation", but intense estimating won't make you hit xmas. Not estimating may give you several weeks that you could be coding.

Either way you're takin a mighty big risk when you publicly commit to that. Welcome to hell, population: Dev Team. I've known of no major software project that has a public date that hasn't resulted in major delays, feature cuts, or massive overtime to try and hit that date.

"Or you might have to hit a deadline for compliance with a legal contract."

That is also a suitably terrible position to be in. I recommend you don't take such contracts. Again, your estimates will be wrong. Even if you spend months doing them. Then you're in the same spot.

"Or you may be trying to prioritize two different possible products - without a sense of the effort involved you're lacking one of the parameters you need for such an estimation."

Which delivers most business value? I find it farfetched that both are of equal importance.

swalkergibson• 14 years ago

How does this apply in an agency context? I would like to see if this can be applied to my company, but I am a little fuzzy on how this theory can work with paying customers who want to get an idea of cost up front.

squirrel2• 14 years ago

I have just moved from B2B, where many "deadlines" were largely artificial and driven by sales targets rather than real business need, to online retail, where the deadline is often concrete, immovable, and external (trade show, Olympics, Christmas). In both environments I found it most useful to encourage my team to commit to completion of _the best solution they can manage_ by a business-meaningful date (picked by the team after suitable consideration, of course). In this model the team do not agree to a specific solution or scope, though to pick the target date at the beginning they usually have an initial solution in mind; as they work toward the date, they (working with the customer representatives in the team) have the freedom to cut features or components, or to add new ones, as they grow in their understanding of the feature and the limitations on delivery (legacy code, lack of experience, unclear business needs). I have generally found that in an environment where development teams are trusted (yes I know such environments are far too rare) this produces results that are as good or better than the recipients expected, and almost always on time or nearly so.

btilly4• 14 years ago

Estimating may be a way to figure out what is plausible to do by Christmas. Which may help you scale your desires up or down to have the best deliverable product that you can.

Also in any contract negotiations, someone has to take the risk. The more risk you take, usually the higher margins you can get. (I am currently working on a contract where my willingness to take on all of the risk of not delivering value has improved my likely profit margins 10-fold.) Thus if you're willing to do fixed schedule and/or fixed price contracts, on average you can charge more. But it would be insane to attempt that without being able to estimate your likely costs and schedules.

Sure, that estimation is an intrinsically hard problem. That is why you get to charge extra for having done it. But it is not trivially the wrong business decision to make.

As an extreme example, I offer you SpaceX. Which signs lots of fixed price bids on development tasks that make the average software project look like a cakewalk.

jt2190• 14 years ago

> It will be done by xmas or it won't.

You claim to be talking about estimation, but I believe that you're actually talking about being given unrealistic, non-negotiable deadlines. (How did we know that the estimate was unrealistic, you ask? We did an estimate.)

gadders3• 14 years ago

The FSA (and other regulatory organisations) frequently give a set date when a feature (EG Souped up trade reporting or similar) needs to be in place by.

Someone• 14 years ago

"your estimates will be wrong. Even if you spend months doing them. Then you're in the same spot"

If you spend months doing estimates you will never do "nothing else". At the very least, you will have a much learnt a lot about the problem domain, and thus you will have a better overview of the work to do. You likely also will have discovered a few pitfalls to avoid, and you already will have changed the requirements of the project at the moment when it is cheapest: before you have a pile of code.

gadders3• 14 years ago

I wonder what would happen if the rest of the world took this approach?

Customer: I was thinking of getting an extension built on my house

Builder: OK

Customer: How long would it take and what would it cost?

Builder; Sorry, but to tell you that would slow down the process of building your extension. It will be quicker if I just get on with it and tell you what you owe me at the end.

foobar99• 14 years ago

What would happen? The customer would know beforehand what is true, anyway.

Berlin Brandenburg Airport was estimated to be opened in October 2011, then 2012, and currently 2013. Costs were estimated with 630 million. The current estimate is 1.2 billion.

Not giving an estimate isn't the entire solution, either.

The problem with an airport is that every time a deadline arrives, all you can do is notice that you don't have an airport, yet. You must estimate again (and you're wrong again).

With software you can say: "We're going to give you a shippable version every week. You can cancel the project at any time and you keep what you've paid for so far. We can screw up completely and you still have last week's shippable product."

Personally, I'd love that pay-as-you-go approach for the rest of the world.

dools• 14 years ago

This is the best article on software I've ever read.

iandanforth2• 14 years ago

The flip side of lie-based estimation is arbitrary deadlines.

I'm not the first to notice that work expands to fill the time allotted. There can be real value in setting a hard deadline with almost no regard for difficulty. This eliminates the 'process' overhead and often produces amazing amounts of work in a shorter period of time than anyone would have estimated. I really like working to deadlines because my motivation is inversely correlated to the time till deadline.

freshhawk3• 14 years ago

It might work for you but it's a horrible way to manage people in general.

Motivation by arbitrary imposed deadline is a standard dev nightmare isn't it? I've watched two companies destroy themselves with this tactic.

Personal motivation and goal setting and even team based motivation and goal setting is important, sure, but you better have other motivation techniques ready when your "hard deadline with almost no regard for difficulty" gets completely missed and the team is depressed and bitter about missing it even after all the effort that was put in.

Also, your team isn't stupid (hopefully). So when they bust their asses to hit that deadline and the next day nothing happens, because it was arbitrary, they learn not to listen to your deadlines.

iandanforth2• 14 years ago

Good point, I was assuming this was done transparently. In the same way that contests are run, a date is chosen, announced and then met with the full knowledge that pride and perhaps a reward are on the line.

Also this can't be the only way you set deadlines as any team would rapidly burn out.

jacques_chester7• 14 years ago

In one of DeMarco's other books -- I can't now recall if it was PeopleWare or The Deadline -- he explains how arbitrary deadlines come unstuck.

Because people learn that they are arbitrary. When the Super Serious Urgent Red Alert All Hands Man Battle Stations deadline whistles by without much more than a frown from management, the team quickly realises that it was total horseshit to begin with.

Software engineers are, it has been observed, a smart bunch. If deadlines are being used a "motivational" technique, they are quickly degraded into meaninglessness.

Which will hurt the company when an actual hard deadline pops up.

Boy who cried "Wolf!" and all that.

ljw10012• 14 years ago

The cost of those hard deadlines is often extra bugs that delay the actual launch date. But they make everybody feel like they're doing some serious management. ;)

X42• 14 years ago

"The roughness of the fractal dimension of a problem that needs to be solved can be calculated more easily in my opinion than with classical estimation techniques."

We're always applying the Roman "divide and conquer" strategy without thinking about it. It wouldn't make sense to apply this, or any other strategy ignorantly! The D&C strategy works because a naive solution to count the fingers in this picture without knowing the fractal dimension is: "divide and conquer". http://mark.rehorst.com/Bug_Photos/fractal_hands_c.jpg (mirror: http://i.minus.com/ibz9NsZ6ET32aV.jpg )

I think this is also the reason why some autistic people feel uncomfortable when they don't know each detail of a not yet happened situation in advance. Because communicating the fractal dimension, or "roughness" of a problem or situation is the most time consuming and fragile phase in a project.

Here's an article about: "Roughness of fracture surfaces and compressive strength of hydrated cement pastes", which appears to be completely out of topic. But I believe it's nearer to the best estimation technique than other techniques. (Fig. 3) http://www.sciencedirect.com/science/article/pii/S0008884610...

While you may critique that I've not contributed to solving the problem, you may also notice that I've helped to shed some light on the roughness of the problem to be solved :) (Am lazy, it's very late and I'm just back from training to be honest=)

X42• 14 years ago

Hey cool, I've found a solution :)

The Fractal Planning Solution – Jim Stone, PhD. PDF http://www.fractalplanner.com/clear_mind.pdf He also offers a hosted planning tool.

James Theiler has found a formula on estimating the fractal dimension. See Google Doc: http://tinyurl.com/cantjjp

akeefer2• 14 years ago

There are two serious problems with this post, and it really saddens me that I see these sorts of posts so frequently here, with so many concurring voices.

First of all, cost absolutely 100% has to factor into prioritization decisions. That doesn't require absolute estimation, but it does demand relative estimation (which he mentions tangentially at the end of the post). If Feature A will deliver $100,000 in revenue but take 18 months and Feature B will deliver $10,000 in revenue but take 1 week, the choice is pretty obvious. What matters is never "return" but always "return on investment." If you don't know anything about the I side of the ROI equation, you're doomed to make bad decisions. With no estimate at all, and just a snarky "it'll take as long as it takes, shut up and let me work" response, you'll inevitably focus on the wrong things.

Secondly, many of us do in fact have deadlines, and they're not just total BS. If you have a customer that you're building something for, they have to be able to plan their own schedule, and just telling them "well, maybe we'll ship it to you in 10/2012 or maybe in 6/2013, you'll get it when you get it" doesn't fly. And it's totally reasonable that it doesn't fly: if they have to, say, install the software, or buy hardware to run it on, or train users, or migrate data from an old system, or roll out new products of their own that are dependent on the new system, they clearly can't plan or budget those activities if they have no clue whatsoever when they'll get the new system.

And if you do have a deadline, you kind of want to know, to the extent that you can, if you're going to make it or not so you can take corrective action (adding people, cutting scope, pushing the date) if need be. You can't do that if you have no estimates at all.

Relative estimation of tasks with empirical measurement of the team's velocity works pretty well; it doesn't work in all cases, but it's pretty much always better than absolutely nothing.

There's a huge, huge difference between doing relative point-based estimation and date-driven, pointy-haired-boss estimation, and it's a total disservice to the software community that so many engineers seem to not really understand that difference, and seem to think that the only two options are "unrealistic date-based estimates" and "no estimates."

TL;DR - Don't just rant for 3000 words about how estimation is horrible and then add in one sentence about relative estimation. You'll do the world much more good if you just help educate people how to do things the right way and spare the ranting.

five18pm• 14 years ago

You took the words out of me.

Even if there are no external customers waiting for the release, a business' other departments have to plan their activities. When will marketing start their pre-release activities without engineering's estimates? When will sales start talking to customers about the new release? There is just too many things that need engineering's estimates.

jacques_chester7• 14 years ago

> There's a huge, huge difference between doing relative point-based estimation and date-driven, pointy-haired-boss estimation, and it's a total disservice to the software community that so many engineers seem to not really understand that difference, and seem to think that the only two options are "unrealistic date-based estimates" and "no estimates."

This was my beef with the article too. Basically on the one hand he proposes a strawman composed of known-worst practices (estimate-by-deadline, estimate-by-gut, ad hoc estimation and so on) and thereby tars all estimation with the brush ... except for the one alternative he approves.

This is the fallacy of dichotomy.

The root problem is the concept that estimates have to be accurate. Well, duh, they can't be. The bigger the project, the more people, the longer the timeframe, the less likely the project is to meet the estimate.

That's why you don't perform one estimate.

That's why you have confidence bands on estimates.

The whole blog article feels like a pastiche of criticism cribbed from agile books and not from a direct, thoughtful engagement with the primary or secondary literature on software project estimation.

I'm only 31. By any measure I'm still a young man. Why do I feel like such a curmudgeon all the time? Because apparently nobody reads books or papers any more. It's all blogs citing blogs who echoed the summary of the notes of the review of a single book.

One more thing. There's a difference between a plan and an estimate. Plan-and-control is not the same thing as performing an estimate; DeMarco's self-criticism is not directly applicable.

jwhite2• 14 years ago

I agree. What would you recommend as a good modern book on software estimation?

arohner2• 14 years ago

> What matters is never "return" but always "return on investment."

You're right. This is one of the primary advantages of startups with technical founders that talk to customers. Among many other flaws of the "OfficeSpace" work environment, one of the biggest is the fact that no single person in the organization knows 1) what is possible to build 2) how much it will cost to make and 3) what is the value of product to the customers.

At my last corporate job before I founded a startup, the CEO didn't know which software was possible to write, and didn't know which new features were easy vs. hard. The marketing people rarely told engineers what the customer wanted, and the engineers didn't talk to customers, and didn't know the cost (or value) of their time.

If there are any well-tested rules for producing good software, they're 1) small teams, 2) technical people with authority and responsibility, 3) talk to the customer.

yason• 14 years ago

But it's already established that deadlines are moot. So giving a deadline for planning, training, and hardware merely reduces to a random guess.

They'd be better off telling the client the truth that "We don't know a honest date and we don't want to lie and come up with an arbitrary one. I can only say it's unlikely that the project would take more than six months and you should at least be prepared to order the hardware by the early summer. We'll keep you posted."

Emphasis on the last part.

Schedules are more accurate later on when some work has been done already. Instead of creating an arbitrary point in the future keep the customer posted with: "We've already finished X and Y in the first month, so we'll soon start working on Z which is a big task but on the other hand we noticed that we don't have to do Q at all since we can just build it in terms of X and Z combined which won't take more than a week instead of the month that was originally planned."

If you tell this every week then everybody has an up-to-date view of the runway ahead. You can also give a "deadline", like: "If you need a deadline for higher-ups or administrative planning, use October 31st but tell them to prepare to plunge in earlier. We all know we'll be done then by a far margin."

Most customers that I've ever had have intuitively understood this is how it works, even if they had to have a "deadline". YMMV.

jbrechtel2• 14 years ago

Are you agreeing with the premise of the article? (It's not clear if you are or if you're just disagreeing with the GP).

If you are then... "We'll keep you posted." "up-to-date view of the runway ahead."

Where do these things come from if you're not estimating effort?

arkitaip• 14 years ago

So what do you do as a freelancer working on projects that last weeks or months? Tell your clients to go screw themselves, that you'll be ready when you're ready?

mbell• 14 years ago

You tell them to define a minimal feature set, and impose that it is actually minimal. This feature set you estimate and give a hard deadline on. Then you tell them that you will iterate based on feedback and add features as directed until such a time as they choose to stop paying you. There is no such thing as "done" in software development.

jasonhanley2• 14 years ago

'There is no such thing as "done" in software development.'

Exactly! That's what makes it so different from physical world projects. You can keep adding/changing things forever.

tmoertel• 14 years ago

Software effort estimation causes three problems. First, most estimation processes model the uncertainty about the effort required for tasks but fail to model the uncertainty about the tasks themselves, leading to unreliable estimates. Second, people are overly confident of the estimates, in any case, because the estimation process looks impressive and produces impressive looking artifacts. Third, the estimation artifacts obscure the coupling between the stakeholders and the implementers by not transmitting how the one group’s decisions affect the other; the estimates, in effect, form a barrier that makes it harder for people on opposites sides of the estimates to take shared responsibility for business goals.

If you understand these problems and can solve them for your projects, estimation can help you to make better decisions and to allocate your resources more effectively. But, in a lot of organizations, these problems have no good solutions (for cultural reasons), and there you might be better off not sharing your estimates if you do them.

URSpider94• 14 years ago

@akeefer nailed it. This is an essay about why project management is bad, written by someone who it seems like has never actually studied project management.

Good planning and estimation is the tool of the worker, not of management. It keeps pointy-haired bosses from coming in and asking "is it done yet?" When done properly, it help justify the number of resources that will be needed to deliver the project on time, and the amount of cash/resources that it will take to complete the project. Good project management results in a not-to-exceed date that is 90% confident (only 10% of projects will exceed this date), so the team has time to tackle unknowns that pop up along the way.

And, yes, at the end of the day, project management is a tool for accountability. Like it or not, everyone has to be accountable for their performance at the end of the day, whether as parents, life partners, or employees. Saying that you don't want to be held accountable by some stupid boss is naive and unrealistic.

freshhawk3• 14 years ago

"the tool of the worker, not of management"

If you have a stereotypical corporate antagonistic divide between workers and management then I completely agree. Good planning and estimation is about managing upwards and managing expectations.

If you are in the context that this post was about, with no or very little divide between management and workers, where blame for delays or praise for being ahead of schedule is equally or nearly equally shared among everyone it's quite a good essay imo.

mille562• 14 years ago

FYI: Flights are on-time if they are within 15 minutes of their scheduled arrival. Arriving 16 minutes early is not an on-time flight.

MattRogish5• 14 years ago

"A flight is counted as "on time" if it operated less than 15 minutes later the scheduled time shown in the carriers' Computerized Reservations Systems (CRS). Arrival performance is based on arrival at the gate. Departure performance is based on departure from the gate."

http://www.bts.gov/help/aviation/index.html

meej• 14 years ago

I'm still reading the essay -- I had to stop and comment about the following paragraph:

"This results in folks that think adding more developers to a project at the beginning will allow them to hit an arbitrary date by spreading out the workload. Unfortunately new software doesn’t work this way, either, as the same exponential communication overhead occurs in the beginning, too. You merely end up with a giant mass of incoherent code. And you waste a lot of money employing people who don’t add much value, sitting on the bench waiting for their part of the project to begin."

These must be folks who stopped reading The Mythical Man-Month after chapter 2? I would think the following chapter about The Surgical Team would counter such thinking. Unless people are only taking away the lesson about the programmer productivity gap?

mistercow2• 14 years ago

>In machine learning, overfitting generally results from having too much test data or focusing on irrelevant metrics.

Huh? Overfitting usually happens when your training set is too small. The size of the test set does not affect overfitting because the test set is, by definition, only used to evaluate the accuracy of the final learned function.

In addition, overfitting doesn't happen because of "focusing on irrelevant metrics". It happens because your data set is noisy, or because your learning model is too simplistic to fully model the observed phenomenon (which is known as deterministic noise).

If your model focuses on irrelevant metrics, that won't actually be a problem as long as your training set is large enough to reveal their irrelevance. After training, those metrics will not have much bearing on the output function.

This misinterpretation of overfitting really hurts the analogy.

MattRogish5• 14 years ago

You're right, I had a brain hiccup with respect to the test/training sets (I used it correctly later on). However, it was my understanding that too many attributes can cause overfitting, and the wiki article suggests this, too. Where am I wrong?

"Overfitting generally occurs when a model is excessively complex, such as having too many parameters relative to the number of observations. "

http://en.wikipedia.org/wiki/Overfitting

mistercow2• 14 years ago

> I had a brain hiccup with respect to the test/training sets (I used it correctly later on).

Just to be clear, it's not just that you said "test data" instead of "training data", but that you said that too much is a bad thing. More data is always a good thing for ML.

[Edit: Actually, there are times where it may not be. If you're doing something like image classification and your data is being created by hand qualitatively, you can actually get overfitting from adding data. As far as I understand, this is because the measurement based on fuzzy perceptual qualities is biased, so the algorithm will overfit to that bias. Maybe this applies with your analogy; I'm not sure.]

>"Overfitting generally occurs when a model is excessively complex, such as having too many parameters relative to the number of observations. "

Well, that's in reference to overfitting as it applies to statistical models, not machine learning. To apply that reasoning to machine learning you have to look at the output of the machine learning algorithm rather than the parameters fed into the algorithm itself. That is, an overfit learned function will often be characterized by excessive complexity, but this is not a result of telling the learning ML algorithm to look at too many parameters. It's a result of telling the ML algorithm to train for too long given the size of its training set.

A key point to note is that an overfit function can be excessively complex even based on very few input parameters if it builds the learned function out of overly complex relationships between those parameters. Conversely, it can build a very simple function, even if many of the parameters prove to be irrelevant, by simply not making the learned function depend on those parameters at all.

aut0mat0n1c• 14 years ago

Using the phrase 'considered harmful' in the title of a blog post is considered harmful

stcredzero• 14 years ago

Comments using the phrase "using the phrase" considered as harmful as comments using the phrase "considered harmful." :)

ljw10012• 14 years ago

I've spent a fair amount of time criticizing the way estimates are done (for example: http://deathrayresearch.tumblr.com/post/4503505772/the-patho...) but although I empathize, this post missed the flight deck completely.

First, as other have pointed out, sometimes estimates are needed (If the guys at YouTube finish their work for the Olympics next month, they have a problem.)

Second, if people only work on software where there's a clear a 50 to 1 payback (as the post suggests), there would be demand for about 10,000 programmers in the world. Competition forces most companies to fight for small, temporary advantages in their products and for incrementally lower costs with their backend systems. (And this ignores entirely the relationship between time to market and returns. Sometimes software is worth a lot if you could have it today, not so much a year from now.)

Third, story points? Not the panacea they're made out to be. I wrote a post on that, too, but one self-referential link is enough for one comment.

Finally, if you're not going to estimate a completion date, why estimate at all? The reasons he gives for estimation are actually reasons to spend time on design. Estimation done that way adds nothing.

sharingancoder• 14 years ago

Agreed! No real point throwing out random estimations instead of actually sitting down and writing the code

drawkbox• 14 years ago

Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law

Parkinson's Law: Work expands so as to fill the time available for its completion.

There is always some probability that software estimation is wrong no matter how well planned out. The greater the size/scope, amount of people and the bigger the timeline is the more chance it will be late.

Like Valve Time proves (https://developer.valvesoftware.com/wiki/Valve_Time), sometimes product trumps time you put in and making games is hard. Sliding deadlines are the most successful because they take into account reality of changing scope/product during development. Or short task sprints/windows like week long or month long product delivery stretches with complete task freedom in between.

Software estimation is hard because there are so many factors and it is a constant ship vs quality balance.

scotty79• 14 years ago

Perfect system for me as a software developer:

1. When considering what is to be done, ask me to asses how hard it is in points. Also ask me to tag the task with words that I consider important like "database schema change" or "attach legacy system" or "IE7" or "find third party library". You can also ask me about additional things like, what subsystems I think I'll have to touch or source written in what languages I think I'm going to touch.

2. Use the prior knowledge of how long similarly hard, similarly tagged tasks took to guess how long this task will take, but do not tell me that because I'm not really the one that is interested.

3. If I'm given any input from people who want to get this done ask me how it changes hardness of the task and the tags.

4. After the task is done ask me again about same things and update your knowledge according to measured time the task was actually worked on, my initial predictions of initial hardness and tags and my final evaluation of actual hardness and tags and any other information you chose to gather.

Worst thing you can do to get an estimate is just ask me how long will it take. I'd rather you, not I make the WAG because then everyone is aware of the fact that it's a WAG.

DanielBMarkham• 14 years ago

As akeefer pointed out, this was a long rant which finally got to the point: separate effort and scheduling. Take a quick chop at estimating effort, but not in terms of duration/dates on a schedule. Relative size works fine. It's better to take a quick hit at estimation over and over again as you begin to see empirical results than it is to spend a lot of time up-front trying to do the perfect estimate.

Software management is not like programming. It's also not like other kinds of management. Any group of people needs some sort of management function. The trick is to put in the most lightweight structure possible. For some reason many technical people of great intelligence, when faced with planning activities, begin to construct various kinds of paper and mathematical wonderlands to live in. We naturally enjoy creating complex models.

Don't do that.

emjimenez• 14 years ago

In a 2001 article, J.P. Lewis demonstrated using the Kolgomorov-Chaitin-Solomonov noncomputability theorem that there are large limits to software Estimation:

http://scribblethink.org/Work/kcsest.pdf

Algorithmic complexity is not computable, then:

1. Program size and complexity cannot be feasibly estimated a priori. 2. Development time cannot be objectively predicted. 3. Absolute productivity cannot be objectively determined.

In fact, Software Estimation methods have an error margin of 100-400% (see Kemerer, C. 1987: An Empirical Validation of Software Cost Estimation Models").

Software Effort Estimation is harmfull because trusting in anything with a 400% margin of error is risky.

gadders3• 14 years ago

As a PM, the other reason developers (or anyone else) doesn't like making estimates:

1) it's hard 2) you are accountable for them

No "My dog ate my homework" type excuses, no leaving at 5pm for a week and telling me on the last day your work will be late.

When you make an estimate, you are putting your credibility on the line. No-one is 100% perfect, but you should at least give meeting the given dates a solid try. Not "Whoops, didn't make it, can I have another week please?"

ken• 14 years ago

I think there's more to it than that. There are other things I do which are hard, and hold me accountable, but which are not painful in the way that software estimation is.

The difference that I see is that software estimation has a third component: lack of control. Every couple days Alice is going to stop by and say "you know we need feature XYZ, too, right?" (which was never in the spec). Then I'm going to overhear at lunch that Bob rewrote the account-management system so I need to rewrite part of my code to integrate with that new interface. And Charlie is going to walk into my office 3 times a day and say "hey, did you see the new video game?". Oh, and this release we're also upgrading to a new version of the foobar library, which works fine for everyone else but mysteriously crashes on my machine, so I spend a day and a half fighting that.

I love being held accountable for hard things. (2 quickdraws on the side of the cliff that I need to retrieve? Great! I'm performing a solo next week and I need to get up to speed on something I've never played before? Bring it on!) But only if I'm being held accountable for something I have control over. Accountability - control = pain.

See also: traffic jams, delayed flights.

Software Effort Estimation Considered Harmful

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