Advanced BioPSE

NCRR

Dynamic Compilation

Joint Session #1: AdvancedBioPSE/SCIRun

Advanced BioPSE

NCRR

C++ BackgroundInheritance • Virtual methods

• Overloaded behavior• gen_fld_ptr->interp(Point *p);• Each field inherits from base and overloads their own

interp appropriate to the field

Templates• Compile time 'virtual'• Interp<FLD>(Point *p);

• Compiler provides replacement for FLD with exact field type at compile time

Advanced BioPSE

NCRR

Field Design

Field Design Library

Must have uniform interface to Fields• Algorithms can be general• Coders can expect uniform interface

Evaluate the following:• Inheritance and virtual methods• Template classes implementing field concept

Advanced BioPSE

NCRR

Templates vs. Virtual

10.21

2.84

30.43

10.1

0

5

10

15

20

25

30

35

MIPSpro 7.3.1.2m GNU g++ 3.0.0

Virtual Template

Test identical functions configured within a virtual method against a templated configuration.

Execution times in seconds

Advanced BioPSE

NCRR

SCIRun Fields

Fields and Meshes are Templated Datatypes that adhere to their concepts

• TetVolField<double>• LatVolField<Tensor>• Many more...

Modules implement algorithms• Multiple Inputs and outputs• Essentially algorithms parameterized on their

inputs and outputs

Advanced BioPSE

NCRR

Template Drawbacks

Template code tends to propogate

All permutations must be known at compile time

Not runtime extensible

SCIRun modules must discover the type• Ports pass all fields as base class type

• Massive amounts of type identification code

• Code maintenance nightmare

Advanced BioPSE

NCRR

Type DiscoveryAlgo dispatch1(FieldHandle field1, callback) { string disp_name = field1->get_type_name(0); if (disp_name == "TetVol") { // test all supported sub types if (field1->get_type_name(1) == "double") { TetVol<double> *f1 = 0; f1 = dynamic_cast<TetVol<double>*>(field1); if (f1) { return new ModuleAlgorithm<TetVol<double> >; } } else if { // The same for the rest of the TetVol types.

•TetVol<int>

•TetVol<unsigned int>

•TetVol<char>

•TetVol<unsigned char>

}

} else if (disp_name == "LatticeVol") { // test all supported sub types } else if (disp_name == "ContourField") { // test all supported sub types } else if (disp_name == "TriSurf") { // test all supported sub types } else { cerr << "Error: Field type not supported" << endl; }}

•TetVol<short>

•TetVol<unsigned short>

•TetVol<Vector>

•TetVol<Tensor>

Advanced BioPSE

NCRR

CombinationsField Types (4)

• TetVolField• LatVolField• TriSurfField• CountourField

Data Types (9)• double• int• Char• float• etc...

An Algorithm Parameterized on One Field Type

• Requires 36 Field instantiations

• And 36 Algorithm Instantiations

Advanced BioPSE

NCRR

CombinationsParameterized On

Two Fields• 362 = 1296 Versions of

the Algorithm

Parameterized On Three Fields

• 363 = 46656 Versions of the Algorithm

SCIRun supports more Field and Data types

Very few of these combinations are needed by any one SCIRun application

Advanced BioPSE

NCRR

Solution

We only compile the exact types we need• Extend C++ RTTI to determine types using strings• Generate C++ code to instantiate correct templates• Fork a process to compile the code• Dynamically link the resulting shared library• Call into the lib to get an instance of the algorithm• Call a single virtual function in the algorithm, passing in

fields and other required parameters• Execute the intended function, which uses

dynamic_cast to get the known underlying field type

Advanced BioPSE

NCRR

Calling the AlgorithmVoid ShowField::execute()

{ // Get a Field from input field port. field = (FieldIPort *)get_iport("Field"); field->get(field_handle); // Get the input field's type info. const TypeDescription *td = field_handle->get_type_description();

// Get the Algorithm. CompileInfo *ci = RenderFieldBase::get_compile_info(td); if (! DynamicLoader::scirun_loader().get(*ci, rend_algo)) { error("Could not compile algorithm for ShowField -");

return; } RenderFieldBase *rf = dynamic_cast<RenderFieldBase*>(rend_algo); // Let the templated algorithm render this field. rf->render(field_handle, /* any other parameters from gui */);

// Send results downstream...}

No Template Instantiations for the exact algorithm type!

Advanced BioPSE

NCRR

Summary

Customize Compilation• Only the algorithms and types you use are compiled• They are persistent (only create once)

Flexibility/Extensibility• Your Fields in your Package compile with existing

algorithms.

Reduce Code Bloat• Won't swamp your compiler• Smaller libraries• Shorter installation compiles