Glossary · Automation software engineering and architecture
Worst-case execution time (WCET)
Also known as: WCET
German: Maximale Ausführungszeit (WCET)
In real-time systems, the worst-case execution time (WCET) is the longest time a task or piece of code can take to execute on a given hardware platform, considering all possible inputs and execution paths.
- Software engineering
In one sentence
The worst-case execution time (WCET) is the longest time a task can take on given hardware across all inputs and execution paths.
Example
Static WCET analysis shows the position controller task needs at most 180 microseconds on the drive's processor, well within its 250-microsecond period.
How it applies
- Engineering: WCET values feed schedulability analysis. They depend on hardware features such as caches and pipelines, which make exact analysis difficult on modern processors.
- Verification: Measurement gives observed maxima, which may underestimate the true worst case. Static analysis tools give safe upper bounds for supported processors. Combining both with a margin is common practice.
- Documentation: Record WCET values, the method used and the conditions in the design documentation. When code or hardware changes, the values must be re-established.
WCET vs. response time
WCET is the execution time of one task alone. Its Response time also includes waiting for higher-priority tasks and blocking, so the worst-case response time is usually larger than the WCET.