engine_graph_scratchpad.h File Reference

Scratchpad implementation for the GraphEngine using CppAD automatic differentiation. More...

#include <vector>
#include "gridfire/engine/scratchpads/scratchpad_abstract.h"
#include "gridfire/engine/scratchpads/types.h"
#include "gridfire/engine/engine_graph.h"
#include "gridfire/engine/engine_abstract.h"
#include "cppad/cppad.hpp"
#include <optional>

Include dependency graph for engine_graph_scratchpad.h:

This graph shows which files directly or indirectly include this file:

Classes
struct	gridfire::engine::scratch::GraphEngineScratchPad
	Scratchpad for storing CppAD automatic differentiation state for GraphEngine. More...

Namespaces
namespace	gridfire
namespace	gridfire::engine
namespace	gridfire::engine::scratch
	Scratchpad memory management for computational engines.

Detailed Description

Scratchpad implementation for the GraphEngine using CppAD automatic differentiation.

This header defines the GraphEngineScratchPad, a concrete implementation of AbstractScratchPad designed for use with the GraphEngine. It provides thread-local storage for CppAD automatic differentiation functions, Jacobian computation work structures, and cached derivatives used during ODE integration.

Purpose

The GraphEngineScratchPad stores:

• A local copy of the CppAD ADFun for RHS evaluation
• Work structures for sparse Jacobian calculations
• Cached abundance values for efficient reuse
• Cached step derivatives and Jacobian subsets by timestep
• The most recent RHS calculation for warm-starting

Examples

#include "gridfire/engine/scratchpads/engine_graph_scratchpad.h"
#include "gridfire/engine/engine_graph.h"
 
// Create and initialize the scratchpad from a GraphEngine
gridfire::engine::scratch::GraphEngineScratchPad scratch;
GraphEngine engine = create_graph_engine();
scratch.initialize(engine);
 
if (scratch.is_initialized()) {
    // Access the local ADFun for thread-safe evaluation
    auto& adfun = scratch.rhsADFun.value();
 
    // Use cached Jacobian work for efficient sparse computations
    auto& jac_work = scratch.jac_work;
}
 
// Clone for parallel execution
auto worker_scratch = scratch.clone();

Thread Safety

This class is not thread-safe. Each thread must have its own instance of GraphEngineScratchPad because CppAD ADFun objects maintain internal state that is modified during evaluation. Use clone() to create independent copies for parallel workers, ensuring each thread has its own ADFun instance.

See also

AbstractScratchPad

GraphEngine

CppAD::ADFun