ngspice_dart

A native Dart port of the ngspice SPICE circuit simulator. Netlist parsing, Modified Nodal Analysis (MNA) assembly, the Newton–Raphson nonlinear solver and the OP / DC / transient / AC analyses all run in pure Dart — there is no FFI, no native library to compile, and no platform-specific build. It runs anywhere Dart runs: Flutter (all platforms), server, CLI, and the web.

This package was previously a thin FFI binding to the C libngspice. It has been reimplemented as a self-contained Dart simulation engine. The original Ngspice facade (init / command / circuit / getVector) is preserved for backwards compatibility.

What's implemented

Area	Support
Elements	Resistor R, Capacitor C, Inductor L, independent V/I sources, Diode D, VCVS E, VCCS G
Source waveforms	DC, AC mag/phase, SIN, PULSE, PWL
Analyses	.op, .dc sweep, .tran (Backward-Euler / Trapezoidal), .ac (dec/oct/lin)
Solver	Dense LU with partial pivoting; Newton–Raphson with pnjlim junction limiting and gmin
Parsing	SPICE engineering suffixes (k, meg, u, n, p, …), + continuations, */;/$ comments, .model D, .ic, .options

This is a meaningful, growing subset of ngspice — not yet the full device library (BJTs, MOSFETs, transmission lines, etc.). Contributions of additional device models stamp cleanly onto the existing Device interface.

Usage

import 'package:ngspice_dart/ngspice_dart.dart';

void main() {
  final ngspice = Ngspice();

  // Load a circuit from netlist lines.
  ngspice.circuit([
    'RC low-pass',
    'V1 1 0 dc 0 ac 1',
    'R1 1 2 1k',
    'C1 2 0 159.155n',
    '.ac dec 10 10 100k',
    '.end',
  ]);

  // Run the declared analyses.
  ngspice.command('run');

  // Retrieve results.
  final mag = ngspice.getVector('v(2)');          // magnitude (AC)
  final cplx = ngspice.getComplexVector('v(2)');  // full complex vector
  print('Gain at first point: ${mag!.first}');
}

Native engine API

For multiple result plots, the parsed circuit, and complex AC data, use [NgspiceEngine] directly:

final engine = NgspiceEngine();
engine.loadCircuit(netlistLines);
engine.run();

final result = engine.currentResult!;   // SimResult: sweep + named vectors
final time = result.sweep;               // independent variable
final vout = result.realVector('v(out)');

See example/ngspice_example.dart for a tour of OP, transient and AC analysis.

Running

dart pub get
dart test
dart run example/ngspice_example.dart