5 ms·

If resources are utilized a 100%, the system will run slower than when there's some slack built in. "The Goal" [1] does a good effort of explaining the theory

If resources are utilized a 100%, the system will run slower than when there's some slack built in. "The Goal" [1] does a good effort of explaining the theory of constraints. [1] https://en.m.wikipedia.org/wiki/The_Goal_(novel) https://en.m.wikipedia.org/wiki/The_Goal_(novel)

kqr 4y ago
My main gripe with Goldratt's ideas is that they are based on the hypothesis that globally analysing a system's averages gives information about bottlenecks and constraints that can be usel to control ingress. It's true for simple systems, and for complex ones better than nothing, of course, but as anyone who has ever run a large system has experienced, the global bottlenecks and the actual, dynamic behaviour of the system at a local level can be quite different. Both demand and capacity can fluctuate unpredictably as people get sick, machines break down, large orders come in, bugs are found, requirements change, and so on. Any optimisation needs to react dynamically to these changing conditions, and changes need to happen locally first and then spread upstream, rather than upstream being globally controlled by the current bottleneck. If you react to bottlenecks only at ingress, you will have large batches traveling through the system only to pile up at the bottleneck anyway, because by the time you choke ingress, large batches that were let through before the bottleneck changed will be making their way through the system unrestricted anyway. Similarly, when a bottleneck goes away, it will take longer for the system to recover if your only control point is globally at ingress. There's a great example of this which I've forgotten where I found it -- could be in the Reinertsen book referenced elsewhere in this discussion. But basically WIP constraints as backpressure outperform global constraint analysis even in quite trivial situations, simply because it adapts more dynamically to the local conditions of the bottleneck and it's surroundings.

kqr 4y ago

My main gripe with Goldratt's ideas is that they are based on the hypothesis that globally analysing a system's averages gives information about bottlenecks and constraints that can be usel to control ingress. It's true for simple systems, and for complex ones better than nothing, of course, but as anyone who has ever run a large system has experienced, the global bottlenecks and the actual, dynamic behaviour of the system at a local level can be quite different. Both demand and capacity can fluctuate unpredictably as people get sick, machines break down, large orders come in, bugs are found, requirements change, and so on. Any optimisation needs to react dynamically to these changing conditions, and changes need to happen locally first and then spread upstream, rather than upstream being globally controlled by the current bottleneck. If you react to bottlenecks only at ingress, you will have large batches traveling through the system only to pile up at the bottleneck anyway, because by the time you choke ingress, large batches that were let through before the bottleneck changed will be making their way through the system unrestricted anyway. Similarly, when a bottleneck goes away, it will take longer for the system to recover if your only control point is globally at ingress. There's a great example of this which I've forgotten where I found it -- could be in the Reinertsen book referenced elsewhere in this discussion. But basically WIP constraints as backpressure outperform global constraint analysis even in quite trivial situations, simply because it adapts more dynamically to the local conditions of the bottleneck and it's surroundings.