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Configure & Run

The Configure & Run workflow lets you build a scenario interactively, submit it to the backend, and visualize results immediately. This page provides a full walkthrough of the configuration form.

Basic Configuration

Configure form

The top section of the form contains four fields that control the core simulation parameters.

Field Type Default Description
Experiment name text my-experiment Identifies this run. Used as the directory name for saved results.
Scheduler select heft Task scheduling algorithm. See options below.
Routing select direct Routing mode for data transfers between nodes.
Seed number 42 Random seed for deterministic reproducibility.

Scheduler Options

Value Algorithm Description
heft HEFT Heterogeneous Earliest Finish Time -- prioritizes tasks by upward rank, assigns each to the node that gives the earliest finish
cpop CPOP Critical Path on a Processor -- identifies the critical path and schedules critical tasks on the fastest processor
round_robin Round Robin Assigns tasks to nodes in a round-robin rotation
manual Manual You assign each task to a specific node using the "Pinned To" column in the DAG section

Routing Options

Value Algorithm Description
direct Direct Uses only explicitly declared links (single-hop). Fails if no direct link exists.
widest_path Widest Path Finds the multi-hop path that maximizes bottleneck bandwidth.
shortest_path Shortest Path Finds the multi-hop path that minimizes total latency (hop count).

Manual scheduler

When you select the manual scheduler, the "Pinned To" column in the DAG Structure section switches from a free-text input to a dropdown populated with all defined node IDs, making it easy to assign each task to a specific node.

Interference Model

Interference config

The Interference Model section lets you select how concurrent wireless transmissions affect each other. The form dynamically shows or hides fields based on your selection.

Available Models

Model Behavior Extra Fields Shown
None No interference. Links use their declared bandwidth at all times. --
Proximity Links within a configurable radius of each other share bandwidth. Radius (m)
CSMA/CA Clique Static clique-based model. Link bandwidth = PHY rate / max clique size. WiFi RF Configuration panel
CSMA/CA Bianchi Bianchi saturation throughput model. MAC throughput derived from collision probability and backoff parameters. WiFi RF Configuration panel

WiFi RF Configuration

When you select either CSMA/CA model, a dedicated panel appears with the following PHY-layer parameters:

Field Default Description
TX Power (dBm) 20 Transmit power
Frequency (GHz) 5.0 Carrier frequency
Path Loss Exponent 3.0 Log-distance path loss exponent
Noise Floor (dBm) -95 Receiver noise floor
CCA Threshold (dBm) -82 Clear Channel Assessment threshold
Channel Width 20 MHz Channel bandwidth (20, 40, 80, or 160 MHz)
WiFi Standard 802.11ax Standard for MCS rate table (802.11n, 802.11ac, or 802.11ax)
Shadow Fading (dB) 0 Standard deviation of log-normal shadow fading
RTS/CTS Off Enable Request-to-Send / Clear-to-Send handshake

RF parameters affect topology generation

When the topology preset is set to "Random (radio-range)", the RF parameters (TX power, frequency, path loss exponent, noise floor) determine the radio range. Links are automatically generated between nodes that fall within this computed range. Changing RF parameters will regenerate the random topology.

Network Topology

Star topology

The Network Topology section defines the compute nodes and communication links of the network.

Topology Presets

Select a preset to auto-generate a topology, or choose Custom to define nodes and links manually.

Preset Shape Link Pattern
Line Chain n-1 sequential links connecting nodes in order
Ring Closed loop n links forming a cycle
Star Hub-and-spoke n-1 links from a central hub to all other nodes
Mesh (fully connected) Complete graph n(n-1)/2 links connecting every pair of nodes
Grid 2D grid Horizontal and vertical links in a grid pattern
Random (radio-range) Position-based Links created between nodes within the computed radio range
Custom Manual No auto-generation; define nodes and links by hand

Topology Parameters

Parameter Range Description
Node count 2 -- 20 Number of compute nodes (slider)
Default capacity 1+ Default compute capacity (CU/s) for generated nodes
Default bandwidth 0.1+ Default bandwidth (MB/s) for generated links

Nodes Table

Each node has the following editable fields:

Column Description
ID Unique node identifier (e.g., n0, n1)
Capacity Compute capacity in CU/s
X X-coordinate position
Y Y-coordinate position

You can add nodes with the Add button or remove individual nodes with the trash icon. When using a preset other than Custom, editing the table switches the mode to Custom.

Each link has the following editable fields:

Column Description
ID Unique link identifier (e.g., l0, l1)
From Source node ID
To Target node ID
BW (MB/s) Bandwidth in megabytes per second
Latency (s) Propagation latency in seconds

DAG Structure

Fork-Join DAG

The DAG Structure section defines the task dependency graph that the scheduler will map onto the network.

DAG Presets

Preset Shape Description
Chain Sequential Each task depends on the previous one, forming a linear chain
Fork-Join Fan-out / fan-in A root task fans out to parallel workers, which all converge to a sink task
Diamond Two-level Root fans to parallel middle layer, which merges, then fans again to a second layer before the final sink
Parallel (independent) Independent All tasks are independent with no data dependencies
Custom Manual No auto-generation; define tasks and edges by hand

DAG Parameters

Parameter Range Description
Task count 2 -- 20 Number of tasks (slider)
Default cost (CU) 1+ Default compute cost in compute units for generated tasks
Default data (MB) 0.1+ Default data size in megabytes for generated edges

Tasks Table

Column Description
ID Unique task identifier (e.g., T0, T1)
Compute Cost Compute cost in CU (compute units)
Pinned To Optional: force this task onto a specific node (used with manual scheduler, or to override any scheduler)

Edges Table

Column Description
From Source task ID (producer)
To Target task ID (consumer)
Data Size (MB) Volume of data transferred between tasks

YAML Preview

YAML preview

At the bottom of the form, a live YAML preview shows the complete scenario definition that will be sent to the backend. This YAML updates in real time as you modify any form field.

The preview includes:

  • Scenario name
  • Full network definition (nodes with positions and capacities, links with bandwidths and latencies)
  • DAG definition (tasks with compute costs, edges with data sizes)
  • Config section (scheduler, seed, routing, interference model, and RF parameters if applicable)

Reusable scenarios

Click the Copy button to copy the YAML to your clipboard. You can save it as a .yaml file and reuse it with the ncsim CLI:

python -m ncsim --scenario my-scenario.yaml --output results/

Running the Experiment

Running

Click the Run Experiment button at the bottom of the form to submit the scenario to the backend.

The backend performs the following steps:

  1. Writes the scenario YAML to a temporary directory
  2. Invokes ncsim as a subprocess with --scenario and --output flags
  3. Reads the generated trace.jsonl and metrics.json files
  4. Returns all three files (scenario YAML, trace JSONL, metrics JSON) to the frontend
  5. Saves the results in viz/public/sample-runs/ for future browsing

Execution time

Simple scenarios (a few nodes and tasks, no interference) complete in under 2 seconds. Complex WiFi scenarios with CSMA/CA Bianchi interference may take longer. The backend enforces a 60-second timeout.

After the run completes successfully, the UI automatically transitions to the visualization view, starting on the Overview tab. If the run fails, an error message is displayed below the Run button with details from ncsim's stderr output.

Backend required

The Run Experiment button requires the FastAPI backend to be running on port 8000. If the backend is not available, the button will show an error. See Viz Setup for instructions on starting both servers.

Next Steps