New feature: hardware querier

[TysonRayJones]

contributor: Tyson Jones
release: v4

QuEST can now report static properties of the hardware to which it is deployed (e.g. the number of CPUs available, the maximum RAM size), and also dynamic runtime properties (e.g. how much VRAM is available). This results from the backend's access to C++ libraries.

• security benefits

  • Whether there is space to (efficiently) store a Qureg can be accessed before memory allocation is attempted, and an error thrown. This avoids encountering an astonishingly slow simulation due to paging effects.

• user benefits

  • Users can query, at runtime, precisely how many qubits their hardware can simulate, without any manual calculation.

[TysonRayJones]

Added in 3e2f782