Improve system ordering

in world.ts, we have the following code, which is in need of more cleverness. It will group most systems by themselves, as it is now, which is very bad, especially once we figure out how to go multi-threaded.

The objective of this story is to get rid of the below mentioned todos.

    // todo: improve logic which sets up the groups
    protected prepareExecutionPipeline(state: IState): Set<TSystemInfo<any>>[] {
        // todo: this could be further optimized by allowing systems with dependencies to run in parallel
        //    if all of their dependencies already ran

        // todo: also, if two systems depend on the same components, they may run in parallel
        //    if they only require READ access
        const result: Set<TSystemInfo<any>>[] = [];
        const stateSystems = Array.from(state.systems);
        let executionGroup: Set<TSystemInfo<any>> = new Set();
        let shouldRunSystem;
        let systemInfo: TSystemInfo<any>;

        if (!this.sortedSystems || this.dirty) {
            // this line is purely to satisfy my IDE
            this.sortedSystems = [];
            this.maintain();
        }

        for (systemInfo of this.sortedSystems) {
            shouldRunSystem = !!stateSystems.find(stateSys => stateSys.constructor.name === systemInfo.system.constructor.name);

            if (shouldRunSystem) {
                if (systemInfo.dependencies.size > 0) {
                    result.push(executionGroup);
                    executionGroup = new Set<any>();
                }

                executionGroup.add(systemInfo);
            }
        }

        result.push(executionGroup);
        return result;
    }

NSSTC / sim-ecs

Improve system ordering #13