This library is in alpha and still under development. First usable version will be v1.1. Note: This library is under heavy development on the dev branch! Forking should mainly be considered for looking around, or contributing of course. At the moment there are some major design flaws which make the Library not less usable but unpractical in the future, these flaws need to be fixed first.

ExecutionGraph

Fast Execution Graph consisting of Execution Nodes

Be able to design and run such input/output dataflow graphs, such as the ones used for the work here (using this graph). A generic, independent GUI is provided in from of a single-page Angular application with a backend HTTP server which allows interactive design/manipulation and execution of graphs:

• ExecutionGraph
  • Installing and Dependencies
    • Library
    • GUI Backend
    • GUI Client
    • Testing
    • OS X
  • Building
• Contributing
  • General Development Setup
    • Codeformatting
    • GUI
  • Introduction
    • Example 1:
• Contributors

Installing and Dependencies

To build the library, the tests and the example you need the build tool cmake. This library has these dependencies:

Library

• meta (meta programming)
• crossguid (guid implementation)
• rttr (runtime type information, serialization only)
• fmt (asserts, exception formatting)

GUI Backend

• args (argument parser)
• memory (memory allocators)
• spdlog (logs)

GUI Client

• node (client build)

Testing

• googletest (for tests)
• benchmark (for benchmarks)

For easy building, all dependencies are searched, downloaded and built if not found, during the first super build run.

OS X

Install the latest clang with homebrew by updateing your xcode installation, installing a code-sign certificate for lldb and then running:

brew install --HEAD llvm --with-toolchain --with-lldb

or manually install

git clone https://github.com/llvm/llvm-project llvm-project
mkdir llvm-build && cd llvm-build
cmake ../llvm-project/llvm -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi;lldb;compiler-rt;lld;polly" -DCMAKE_INSTALL_PREFIX="/usr/local/opt/llvm-latest"
make -j install

Now you should be ready to configure with cmake:

Building

Source the tools/.enable-compiler.sh and use enableCompiler "clang" which uses the tools/.clang-flags-llvm-latest.cfg to setup the compiler before you configure with:

cd <pathToRepo>
mkdir build
cd build
# configuring the superbuild (-DUSE_SUPERBUILD=ON is default)
cmake .. -DUSE_SUPERBUILD=ON \
        -DExecutionGraph_BUILD_TESTS=true \
        -DExecutionGraph_BUILD_LIBRARY=true \
        -DExecutionGraph_BUILD_GUI=true \
        -DExecutionGraph_EXTERNAL_BUILD_DIR="$(pwd)/external" \
        -DExecutionGraph_USE_ADDRESS_SANITIZER=true \
        -DCMAKE_EXPORT_COMPILE_COMMANDS=true
# building the superbuild configuration 
make -j all
# configuring the actual build
cmake ..
# building the library/gui
make -j <targetName>

We use a super build setup. The first cmake configure and build by using -DUSE_SUPERBUILD=ON (automatically set at first run) will download every dependency and build the ones which need installing. See the cmake variable ExecutionGraph_EXTERNAL_BUILD_DIR which is used for building all external dependencies to be able to quickly delete certain dependencies without deleting the normal build folder build). After the super build, the cmake cache file CMakeCache.txt is setup with all necessary variables, that later cmake configure invocations will find all dependencies and configure the actual project. This works also with VS Code and the cmake extension.

Contributing

This project supports Visual Studio Code which is warmly recommended.

Note: Dont use the multi-root workspaces feature in VS Code since the C++ Extension does not yet support this and code completion won't work properly.

General Development Setup

If you start developing, install the pre-commit/post-commit hooks with:

sudo npm install -g json-fmt xmllint prettier
sudo apt-get install plantuml # or sudo brew install plantuml
cd .git && mv hooks hooks.old && ln -s ../tools/git-hooks hooks

Codeformatting

You can run the same pre-commit hook by doing

tools/formatAll.sh

which will format all files for which formatting styles have been defined in the repository.

GUI

The UI is made up of an Angular application that uses the Angular CLI to create the web assets that are ultimately displayed in an electron app browser. The client backend consists of a http server which provides the executiong graph. Please visit the Angular CLI website for its prerequisites (node.js and npm respectively, also a globally installed Angular CLI aka ng). Once you installed the prerequisites build with

cd gui/executionGraphGui/client
npm install
npm run serve

For more information about the development of the client application please refer to the dedicated client documentation

Introduction

The execution graph implemented in ExecutionTree is a directed acyclic graph consisting of several connected nodes derived from LogicNode which define a simple input/output control flow. Each node in the execution graph contains several input/output sockets (LogicSocket) with a certain type out of the predefined types defined in LogicSocketTypes.

An execution graph works in the way that each node contains a specific compute routine which provides values for the output sockets by using the values from the input sockets. Each output of a node can be linked to an input of the same type of another node. This means an output socket of the arithmetic type double cannot be linked to an input socket of integral type int for example. Each node can be assigned to one or more execution groups which are collections of nodes and form directed acyclic subgraphs.

For each execution group, an execution order is computed such that the data flow defined by the input/output links in the group is respected.

An execution order of an execution group is called a topological ordering in computer science, and such an ordering always exists for a directed acyclic graph, despite being non-unique. A topological ordering of an execution group is an ordering of all nodes such that for all connections from a node A to B, A precedes B in the ordering. Each execution graph network consists of several input nodes whose output sockets are initialized before executing the network. The implementation in LogicSocket allows two types of directed links between an input and output socket, namely a get and a write connection.

A write link is a link from an output socket i of a node A to an input socket j of some node B, denoted as {A,i} -> {j,B}. A write link basically duplicates a write request to the output socket i of A also to an additional write request to the input socket j of B.

A get link is the exact opposite and is a link from an input socket j of a node B to an output socket i of a node A, denoted as {A,i} <- {j,B}. A get link basically forwards any read access on the input socket j of B to a read access on the input socket i of A.

Most of the time only get links are necessary but as soon as the execution graph becomes more complex and certain switching behavior should be reproduced, the additional write links are a convenient tool to realize this.

Cyclic paths between nodes are detected and result in an error when building the execution network. The write and read access to input and output sockets is implemented using a fast static type dispatch system in LogicSocket.

Static type dispatching avoids the use of virtual calls when using polymorphic objects in object-oriented programming languages.

Example 1:

Source: examples/libraryUsage
Let us build the simple directed graph below:

This execution tree consists of 4 input nodes, e.g. Node 1a, 1b, 2a, 2b, and 1 output node 4a. Each node has 2 input sockets, e.g. denoted as i0 and i1, and one output socket o0. The type of the input and output sockets in this example is simply int. Each node computes the sum of both input sockets i0 and i1 and stores it in the output socket i1 (of course this is kind of stupid, it is only an example =).

First, we define our node type called IntegerNode<...>:

template<typename TConfig>
class IntegerNode : public typename TConfig::NodeBaseType
{
public:
    using Config = TConfig;
    using NodeBaseType = typename Config::NodeBaseType;
    enum Ins
    {
        Value1,
        Value2
    };
    enum Outs
    {
        Result1,
    };

We start of by deriving our IntegerNode from TConfig::NodeBaseType. The template parameter TConfig lets us configure our execution graph (especially the socket type list). The type TConfig::NodeBaseType is the basis class for all nodes (resulting in LogicNode<Config>). The two enumerations Ins and Outs let us define some handy abbreviations for our input sockets (Value1 and Value2) and our output socket (Result1). The sequential ordering of the enumerations in Ins and Outs does not matter at all! So far so good. Now we use some macro for letting us specify the input/output ordering:

private:
    EXECGRAPH_DEFINE_SOCKET_TRAITS(Ins, Outs);
    // Define the input socket decleration list:
    using InSockets  = InSocketDeclList<InSocketDecl<Value1, int>,
                                        InSocketDecl<Value2, int>>;
    // Define the input socket decleration list:
    using OutSockets = OutSocketDeclList<OutSocketDecl<Result1, int>>;

What we are specifying here is the following: The type InSockets is a socket declaration list which says that the input socket with enumeration value Value1 is of type int and is the first input i0. The second entry defines the second input socket with enumeration value Value2 which is of type int too. The same is done for our output by defining OutSockets.

Now we define two other handy macros:

    EXECGRAPH_DEFINE_LOGIC_NODE_GET_TYPENAME();
    EXECGRAPH_DEFINE_LOGIC_NODE_VALUE_GETTERS(Ins, InSockets, Outs, OutSockets);

The first one is not so important. It only defines some virtual std::string getTypeName() function which demangles the type of this node at runtime (for debugging purposes). The second one defines some handy value-getters and setters for easy access (by means of the enumerations Ins and Outs) to the sockets values (more later).

Let us define the constructor of our IntegerNode<...>:

template<typename... Args>
    IntegerNode(Args&&... args)
        : NodeBaseType(std::forward<Args>(args)...)
    {
        this->template addSockets<InSockets>(std::make_tuple(2,2));
        this->template addSockets<OutSockets>(std::make_tuple(0));
    }

In the constructor, we create (add) the input and output sockets to the node. The parameter std::tuple<...> contains the default (constructor) values for the values stored in the sockets. So in the above snippet, we set the input sockets both to the value 2 and the output socket to the value 0. Next we define the actual computation which is performed when this node is executed:

    void compute() override {
        getOutVal<Result1>() = getInVal<Value1>() + getInVal<Value2>();
    }
}; // end of class declaration

Here we simply add both input values ( getInVal<...>() return a reference) and store the result in the output socket.

Now, let us build the main ingredient of this example: the execution tree. First we allocate the 7 nodes by

using namespace executionGraph; 
int main(){
    using Config = GeneralConfig<>; // we use the default configuration
    
    auto node1a = std::make_unique<IntegerNode<Config>>(0);
    auto node1b = std::make_unique<IntegerNode<Config>>(1);
    auto node2a = std::make_unique<IntegerNode<Config>>(2);
    auto node2b = std::make_unique<IntegerNode<Config>>(3);
    auto node3a = std::make_unique<IntegerNode<Config>>(4);
    auto node3b = std::make_unique<IntegerNode<Config>>(5);
    auto node4a = std::make_unique<IntegerNode<Config>>(6);
    auto resultNode = node4a.get();

Each node is given a unique id [0,...,6], which enables us to identify the nodes easier. Next we create the get links which connect the in- and outputs.

    int i0 = 0; int i1 = 1; int o0 = 0;
    node4a->setGetLink(*node3a,o0,i0);
    node4a->setGetLink(*node3b,o0,i1);

    node3a->setGetLink(*node1a,o0,i0);
    node3a->setGetLink(*node1b,o0,i1);
    
    node3b->setGetLink(*node2a,o0,i0);
    node3b->setGetLink(*node2b,o0,i1);

The syntax node4a->setGetLink(*node3a,o0,i0); denotes that the output node node4a gets its first input value i0 = 0 from the single output o0 = 0 of node node3a. The above snippet builds the execution tree given at the begining. Finally we create the ExecutionTree ExecutionTree, add all nodes to it, set the proper node classfication (if its an input or output node, setup the graph (which computes the execution order) and execute the default execution group 0 as

    // Make the execution tree and add all nodes
    ExecutionTree<Config> execTree;
    execTree.addNode(std::move(node1a)); // The execution tree owns the nodes!
    execTree.addNode(std::move(node1b));
    execTree.addNode(std::move(node2a));
    execTree.addNode(std::move(node2b));
    execTree.addNode(std::move(node3a));
    execTree.addNode(std::move(node3b));
    execTree.addNode(std::move(node4a));

    // Set all node classifications
    execTree.setNodeClass(0, ExecutionTree<Config>::NodeClassification::InputNode);
    execTree.setNodeClass(1, ExecutionTree<Config>::NodeClassification::InputNode);
    execTree.setNodeClass(2, ExecutionTree<Config>::NodeClassification::InputNode);
    execTree.setNodeClass(3, ExecutionTree<Config>::NodeClassification::InputNode);
    execTree.setNodeClass(6, ExecutionTree<Config>::NodeClassification::OutputNode);
    
    // Setup the execution tree
    execTree.setup();
    EXECGRAPH_LOG_INFO(execTree.getExecutionOrderInfo());
    execTree.execute(0); // execute the default execution group (=0)
    EXECGRAPH_LOG_INFO("Result : '{0}'", resultNode->getOutVal<IntegerNode<Config>::Result1>());

This outputs the following execution order:

Execution order for group id: 0
    NodeId  |  Priority  |  NodeType            
    ------  |  --------  |  --------            
         0  |         2  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         1  |         2  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         2  |         2  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         3  |         2  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         5  |         1  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         4  |         1  |  IntegerNode<executionGraph::GeneralConfig<...> >*
         6  |         0  |  IntegerNode<executionGraph::GeneralConfig<...> >*
    ------  |  --------  |  --------  

Contributors

Gabriel Nützi and many thanks to:

• Simon Spörri for his nice and ellaborate take on the client gui application!