What does the beckmarking in global scope mean?

[mbauman]

Check out this previous thread and the linked SO answer

Function calls in global scope, benchmarking, etc

I recently asked a Stack Overflow question about interpolating into benchmarking expressions. But I still have some lingering confusion about the impact on performance of passing global variables as arguments to functions. The Julia manual in the Performance Tips section says A global variable might have its value, and therefore its type, change at any point. This makes it difficult for the compiler to optimize code using global variables. Variables should be local, or passed as arguments to f…

In your example, $ is used to get a sense of the performance of A\b when A and b are either local and type-stable inside a function (including if they’re arguments) or they’re declared as const globals. It’s the former that most folks are interested in when benchmarking because that’s the happy path for high-performance Julia.

You’ve not declared A and b as const, so they’re not constant.