Which Amazon EC2 purchasing option is the most cost-effective for running a continuous simulation for three years?

Reserved Instances (RIs) are the most cost-effective option for a continuous workload over three years because they offer significant discounts (up to 75%) compared to On-Demand pricing in exchange for a commitment to a specific instance type and region for a 1-year or 3-year term. This long-term commitment aligns perfectly with the three-year continuous simulation. Spot Instances are unsuitable as they can be interrupted with two minutes' notice, making them unreliable for continuous workloads. Dedicated Hosts provide dedicated physical servers for regulatory compliance or specific licensing requirements, but they are generally more expensive and not primarily for cost savings on continuous compute. On-Demand Instances offer flexibility but are the most expensive option for long-running, predictable workloads.