Three Hundred Devices Waiting on One
Last timeChoosing Which Split to Use
Poor scaling has three usual causes and they leave different marks on a timeline. Read the marks and you know which one it is without changing anything.
The arithmetic says this layout should run at eighty per cent of the throughput
of a single device multiplied by a thousand. It is running at forty. Nothing is
broken, no error has appeared, and the loss is going down.
Measuring the scaling
Before looking for a cause, make the symptom a number.
- scaling efficiency, where one is perfect
- throughput of the whole run, in examples per second
- throughput of a single device running alone
- number of devices
The three shapes
The three causes are a slow link, an unbalanced split, and one slow device. On
a timeline recorded per device, each one looks different.
The lesson stops here
3 more paragraphs to go
You have read the opening. The rest of the argument, the problems that check whether it landed, and the lines worth keeping at the end all come with a plan.
The first lesson of every course in the library reads the whole way through, free, so you can see exactly what the rest of them are.
See the planThe contentsThis is the reading half
Starting the course gives you your own copy of it. Every idea on every page has problems standing under it, marked with a reason rather than a tick, and any sentence you do not believe can be opened and argued with. None of that can happen on a page nobody owns.
The contents