แนวคิดหลัก
Randomization of implicit two-stage Runge-Kutta schemes can improve the rate of convergence and stability of the approximate solution compared to deterministic schemes.
บทคัดย่อ
The paper investigates two randomized implicit schemes from the two-stage Runge-Kutta family:
- Semi-implicit randomized RK2 scheme: The intermediate step is implicit, while the final step is explicit.
- Implicit randomized RK2 scheme: The slope is calculated at a point chosen randomly from the segment joining the previous and current iterates.
The key findings are:
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Convergence: Randomization helps achieve a better rate of convergence, improving the rate by 1/2 compared to deterministic schemes.
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Stability:
- The randomized implicit RK2 schemes are asymptotically A-stable and A-stable in probability, but not mean-square A-stable.
- The mean-square stability region is bounded, in contrast to the deterministic implicit schemes which are A-stable.
- The randomized implicit RK2 schemes outperform the randomized explicit RK2 scheme in terms of stability.
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Numerical experiments:
- The randomized implicit RK2 schemes exhibit significant but bounded errors, with a tendency to return to the proximity of the exact solution after peaks.
- This behavior is linked to the schemes being asymptotically A-stable but not mean-square A-stable.
Overall, the paper demonstrates that randomization can improve the convergence and stability properties of implicit Runge-Kutta schemes compared to their deterministic counterparts.