Si vous allez sur Google et recherchez “mesurer la productivité des développeurs de logiciels” tu ne trouveras rien. Sérieusement — rien.
Nick Hodges, Measuring Developer Productivity
By now we should all know that we don’t know how to measure programmer productivity.
Il n'y a pas clear cut way to measure which programmers are doing a better or faster job, or to compare productivity across teams. We “know” who the stars on a team are, who we can depend on to deliver, and who is struggling. And we know if a team is kicking ass – or dragging their asses. But how do we prove it? How can we quantify it?
All sorts of stupid and evil things can happen when you try to measure programmer productivity.
Mais faisons-le quand même.
We’re writing more code, so we must be more productive
Developers are paid to write code. So why not measure how much code they write – how many lines of code get delivered?
Because we’ve known since the 1980s that this is a lousy way to measure productivity.
Lines of code can’t be compared across languages (bien sûr), or even between programmers using the same language working in different frameworks or following different styles. Which is why Points de fonction were invented – an attempt to standardize and compare the size of work in different environments. Sounds good, but Function Points haven’t made it into the mainstream, and probably never will – very few people know how Function Points work, how to calculate them and how they should be used.
The more fundamental problem is that measuring productivity by lines (or Function Points or other derivatives) typed doesn’t make any sense. A lot of important work in software development, the most important work, involves thinking and learning – not typing.
The best programmers spend a lot of time understanding and solving hard problems, or helping other people understand and solve hard problems, instead of typing. They find ways to simplify code and eliminate duplication. And a lot of the code that they do write won’t count anyways, as they iterate through experiments and build prototypes and throw all of it away in order to get to an optimal solution.
The flaws in these measures are obvious if we consider the ideal outcomes: the fewest lines of code possible in order to solve a problem, and the creation of simplified, common processes and customer interactions that reduce complexity in IT systems. Our most productive people are those that find ingenious ways to avoid writing any code at all.
Jez Humble, The Lean Enterprise
This is clearly one of those cases where size doesn’t matter.
We’re making (or saving) more money,
so we must be working better
We could try to measure productivity at a high level using profitability or financial return on what each team is delivering, or some other business measure such as how many customers are using the system – if developers are making more money for the business (or saving more money), they must be doing something right.
Using financial measures seems like a good idea at the executive level, especially now that “every company is a software company". These are organizational measures that developers should share in. But they are not effective – or fair – measures of developer productivity. There are too many business factors are outside of the development team’s control. Some products or services succeed even if the people delivering them are doing a lousy job, or fail even if the team did a great job. Focusing on cost savings in particular leads many managers to cut people and try “to do more with less” instead of investing in real productivity improvements.
And as Martin Fowler points out there is a time lag, especially in large organizations – it can sometimes take months or years to see real financial results from an IT project, or from productivity improvements.
We need to look somewhere else to find meaningful productivity metrics.
We’re going faster, so we must be getting more productive
Measuring speed of development – rapidité in Agile – looks like another way to measure productivity at the team level. Après tout, the point of software development is to deliver working software. The faster that a team delivers, the better.
But rapidité (how much work, measured in story points or feature points or ideal days, that the team delivers in a period of time) is really a measure of predictability, not productivity. Velocity is intended to be used by a team to measure how much work they can take on, to calibrate their estimates and plan their work forward.
Once a team’s velocity has stabilized, you can measure changes in velocity within the team as a relative measure of productivity. If the team’s velocity is decelerating, it could be an indicator of problems in the team or the project or the system. Or you can use velocity to measure the impact of process improvements, to see if training or new tools or new practices actually make the team’s work measurably faster.
But you will have to account for changes in the team, as people join or leave. And you will have to remember that velocity is a measure that only makes sense within a team – that you can’t compare velocity between teams.
Although this doesn’t stop people from trying. Some shops use the idea of a well-known reference story that all teams in a program understand and use to base their story points estimates on. As long as teams aren’t given much freedom on how they come up with estimates, and as long as the teams are working in the same project or program with the same constraints and assumptions, you might be able to do rough comparison of velocity between teams. But Mike Cohn warns that
If teams feel the slightest indication that velocities will be compared between teams there will be gradual but consistent “point inflation.”
ThoughtWorks explains that rapidité <> productivité in their latest Technology Radar:
We continue to see teams and organizations equating velocity with productivity. When properly used, velocity allows the incorporation of “yesterday’s weather” into a team’s internal iteration planning process. The key here is that velocity is an internal measure for a team, it is just a capacity estimate for that given team at that given time. Organizations and managers who equate internal velocity with external productivity start to set targets for velocity, forgetting that what actually matters is working software in production. Treating velocity as productivity leads to unproductive team behaviors that optimize this metric at the expense of actual working software.
Just stay busy
One manager I know says that instead of trying to measure productivity
“We just stay busy. If we’re busy working away like maniacs, we can look out for problems and bottlenecks and fix them and keep going”.
In this case you would measure – and optimize for – cycle time, like in Lean manufacturing.
Cycle time – turnaround time or change lead time, from when the business asks for something to when they get it in their hands and see it working – is something that the business cares about, and something that everyone can see and measure. And once you start looking closely, waste and delays will show up as you measure waiting/idle time, value-add vs. non-value-add work, et process cycle efficiency (total value-add time / total cycle time).
“It’s not important to define productivity, or to measure it. It’s much more important to identify non-productive activities and drive them down to zero.”
Erik Simmons, Intel
Teams can use Kanban to monitor – and limit – work in progress and identify delays and bottlenecks. Et Value Stream Mapping to understand the steps, queues, delays and information flows which need to be optimized. To be effective, you have to look at the end-to-end process from when requests are first made to when they are delivered and running, and optimize all along the path, not just the work in development. This may mean changing how the business prioritizes, how decisions are made and who makes the decisions.
In almost every case we have seen, making one process block more efficient will have a minimal effect on the overall value stream. Since rework and wait times are some of the biggest contributors to overall delivery time, adopting “agile” processes within a single function (such as development) generally has little impact on the overall value stream, and hence on customer outcomes.
Jezz Humble, The Lean Enterprise
The down side of equating delivery speed with productivity? Optimizing for cycle time/speed of delivery by itself could lead to problems over the long term, because this incents people to think short term, and to cut corners and take on technical debt.
We’re writing better software, so we must be more productive
“The paradox is that when managers focus on productivity, long-term improvements are rarely made. D'autre part, when managers focus on quality, productivity improves continuously.”
John Seddon, quoted in The Lean Enterprise
We know that fixing bugs later costs more. Whether it’s 10x or 100+x, it doesn’t really matter. And that projects with fewer bugs are delivered faster – at least up to a point of diminishing returns for safety-critical and life-critical systems.
And we know that the costs of bugs and mistakes in software to the business can be significant. Not just development rework costs and maintenance and support costs. But direct costs to the business. Downtime. Security breaches. Lost IP. Lost customers. Fines. Lawsuits. Business failure.
It’s easy to measure that you are writing good – or bad – software. Defect density. Defect escape rates (especially defects – including security vulnerabilities – that escape to production). Static analysis metrics on the code base, using tools like SonarQube.
And we know how to write good software – or we should know by now. But is software quality enough to define productivity?
Devops – Measuring and Improving IT Performance
Devops teams who build/maintain and operate/support systems extend productivity from dev into ops. They measure productivity across two dimensions that we have already looked at: speed of delivery, et qualité.
But devops isn’t limited to just building and delivering code – instead it looks at performance metrics for end-to-end IT service delivery:
- Delivery Throughput: deployment frequency and lead time, maximizing the flow of work into production
- Service Quality: change failure rate and MTTR
It’s not a matter of just delivering software faster or better. It’s dev and ops working together to deliver services better and faster, striking a balance between moving too fast or trying to do too much at a time, and excessive bureaucracy and over-caution resulting in waste and delays. Dev and ops need to share responsibility and accountability for the outcome, and for measuring and improving productivity and quality.
As I pointed out in an earlier post this makes operational metrics more important than developer metrics. According to recent studies, success in achieving these goals lead to improvements in business success: not just productivity, but market share and profitability.
Measure Outcomes, not Output
Dans The Lean Enterprise (which you can tell I just finished reading), Jez Jumble talks about the importance of measuring productivity by outcome – measuring things that matter to the organization – not output.
“It doesn’t matter how many stories we complete if we don’t achieve the business outcomes we set out to achieve in the form of program-level target conditions”.
Stop trying to measure individual developer productivity. C'est une perte de temps.
- Everyone knows who the top performers are. Point them in the right direction, and keep them happy.
- Everyone knows the people who are struggling. Get them the help that they need to succeed.
- Everyone knows who doesn’t fit in. Move them out.
Measuring and improving productivity at the team or (better) organization level will give you much more meaningful returns.
When it comes to productivity:
- Measure things that matter – things that will make a difference to the team or to the organization. Measures that are clear, important, and that aren’t easy to game.
- Use metrics for good, not for evil – to drive learning and improvement, not to compare output between teams or to rank people.
I can see why measuring productivity is so seductive. If we could do it we could assess software much more easily and objectively than we can now. But false measures only make things worse.
Martin Fowler, CannotMeasureProductivity
A propos de l'auteur
Jim Bird is an experienced software development manager, project manager and currently CTO at a financial services firm. He is focused on hard problems in software development and maintenance, software quality and security. For the last 15 years he has managed teams building and operating high-performance financial systems. His special interest is how small teams can be most effective in building real software: high-quality, secure systems at the extreme limits of reliability, performance, and adaptability. Software that has to work, that is built right, and built to last. This article was originally posted on his own blog Building Real Software.
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et ne coïncide pas nécessairement avec les politiques officielles de Nesma.