Restores the ambient session state a solve may perturb: "a solve leaves the session as it found it". More...

#include <zero_dim_solve.hpp>

Collaboration diagram for bertini::algorithm::HomotopySolver< TrackerType, EndgameType, SystemType >::ScopedSessionState:

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Public Member Functions
	ScopedSessionState ()
	Capture the ambient session state.
	~ScopedSessionState ()
	Restore it, whatever the solve did in between.
	ScopedSessionState (ScopedSessionState const &)=delete
	Non-copyable.
ScopedSessionState &	operator= (ScopedSessionState const &)=delete
	Non-assignable.

Public Attributes
unsigned	precision_
	The ambient default precision at solve entry.
std::mt19937	engine_
	The calling thread's legacy engine state at entry.
records::DrawStream	stream_
	The calling thread's pinned draw stream at entry.

Detailed Description

template<typename TrackerType, typename EndgameType, typename SystemType>
struct bertini::algorithm::HomotopySolver< TrackerType, EndgameType, SystemType >::ScopedSessionState

Restores the ambient session state a solve may perturb: "a solve leaves the session as it found it".

Two globals otherwise leak: the mpfr default precision (an adaptive solve historically left it at the tracking precision – e.g. 16 after a double-fast-lane finish), and the calling thread's RNG streams (serial tracking rekeys them to per-path domains via ReseedThisThread). Either leak makes what a LATER solve computes – its config identity, its drawn coefficients – depend on whether THIS solve computed or recalled, which cascades into phantom new asks on rerun. Scoped restoration makes recall and compute indistinguishable to the rest of the session; the records the solve wrote are its only trace.