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SAPI: What is delta (Δ) time?
The SAPI docs say "...a small amount of additional time (Δ) for low-level operations is not shown." It looks like delta occurs between programming and sampling.
https://docs.dwavesys.com/docs/latest/c_qpu_timing.html
* What is the nature of the low-level operations?
* Is delta constant or variable?
* Does the user influence delta in any way?
* What range of values can delta be?
Comments
Hi Thomas
Delta is a combination of software overhead and communications overhead with the electronics controlling the QPU. It is a distributed time and captures all the time when the QPU is being exclusively held by the submitted job, but not doing anything captured by the other timing variables.
Delta varies depending on system load and other factors and is not directly influenced by the user. It is typically 1-3ms.
Does this answer your question?
I think so -- it sounds like this time is an artifact of the QPU control electronics switching from programming to the annealing process. Something akin to waiting for an RF circuit to stabilize, logic gates to latch, capacitor to charge, the field around an inductor to collapse, heat to dissipate, etc.?
Hi Thomas
No --- the equivalent of the time you describe is the "default_programming_thermalization" and is included in the timing information. "Delta" is all the time associated with software overhead and communications with the rack of electronics controlling the QPU and is not contained only between the programming / annealing process boundary.
Note that there is also a tunable parameter that you can use to adjust the thermalization time: programming_thermalization.
All SAPI properties and parameters for QPU solvers are described here: https://docs.dwavesys.com/docs/latest/doc_solver_ref.html
Thanks - that helps.
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