Temporarily disable/enable Vernier

[hiker]

Many profiling libraries offer the option to (temporarily) disable or enable profiling, eg. to reduce profiling impact in terms of runtime of output file size, or just to focus on a given part of the code. PSyclone's psydata API provides call to these functionality, and I believe Andy is often using it.

While there is no requirement to support this (atm the corresponding PSyclone's psydata API call just don't do anything), I just wanted to suggest this as a potential enhancement.

[mo-mglover]

We wondered about this in the early stages of the project, but I think it's better left to the client code to manage this.

On the negative side, it makes code such as if (flag) call vernier_start necessary, but the postives are:

• If flag is set as a parameter to .false. then the compiler's optimiser will strip out the calls completely, so there's no overhead a production context.
• Client codes are free to define several different flags, which may be specific to particular code sections or relate to the amount of profiling overhead particular regions incur.

[hiker]

I wasn't talking of disabling it entirely. It could be that e.g. you don't want to measure (say) startup, or you only want to measure after 2 days of simulated time (to capture a shift in computational profile because ... something happens). So you would add a call to 'disable' Venier, and once the init is done, you will enable it again.

With PSyclone, by default each kernel will get instrumented, while this can be changed (by using custom scripts for some files), it is way more convenience to just add calls to start/stop to narrow the output to what you are interested in.

The name I used (enabling/disabling) was not ideal - in PSyclone we have calls to PSyDataStart() and PSyDataStop, which will enable/disable a library (if supported). That's why I called it 'temporarily', i.e. for some parts of the runtime.