Function ros3prw

Example

// Example. Solve the following initial value problem using the ROS3PRw method:
//   dx/dt = x + y - t
//   dy/dt = x * y + t
//   x(0) = 1
//   y(0) = -1
// on [0, 2] with the step 0.01.
import { ODEs, ros3prw } from 'diff-grok';

const task: ODEs = {
  name: 'Example', // name of your model
  arg: {
      name: 't',  // name of the argument
      start: 0,   // initial value of the argument
      finish: 2,  // final value of the argument
      step: 0.01, // solution grid step
  },
  initial: [1, -1], // initial values
  func: (t: number, y: Float64Array, output: Float64Array) => { // right-hand side of the system
    output[0] = y[0] + y[1] - t; // 1-st equation
    output[1] = y[0] * y[1] + t; // 2-nd equation
  },
  tolerance: 1e-7, // tolerance
  solutionColNames: ['x', 'y'], // names of solution functions
};

try {
  // Solve the problem using the ROS3PRw method
  const solution = ros3prw(task);

  // Print a table with the results
  console.log(task.arg.name, task.solutionColNames[0], task.solutionColNames[1]);
  const length = solution[0].length;
  for (let i = 0; i < length; ++i)
    console.log(solution[0][i], solution[1][i], solution[2][i]);
} catch (err) {
  console.log('Solver failed: ', err instanceof Error ? err.message : 'Unknown problem!');
}
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