Qwen 3.8 27B on a 3090 with a Sonnet 5.5 as a planner: 2.7x cheaper, real numbers

Qwen 3.8 27B on a 3090 with a Sonnet 5.5 as a planner: 2.7x cheaper, real numbers

Analyzing Cost-Effective Physics Simulation with Qwen 3.8 27B on a High-End GPU in an Autonomous Agent Setup

In the evolving landscape of artificial intelligence-driven simulations, balancing performance, accuracy, and cost remains crucial. Recent experiments have explored leveraging large language models (LLMs) like Qwen 3.8 27B in combination with specialized planning tools to execute physics-based scenes efficiently and affordably. Below is a detailed overview of a practical assessment conducted to determine the viability of such a setup.

Experimental Overview

The core objective was to evaluate whether a locally hosted Qwen 3.8 27B model could effectively handle complex simulation tasks when augmented with a planning agent such as Sonnet 5.5. The experiment involved running multiple configurations, capturing key metrics like scene completion progress, processing time, and associated costs.

Hardware and Software Configuration

  • Local Processing Hardware:
  • Card: NVIDIA RTX 3090 (24 GB VRAM)
  • Model Framework: llama.cpp, built with CUDA support for acceleration
  • Environment Details:

    • Dual parallel computation slots
    • 64K token context window
    • Turbo3 KV cache for performance enhancement
  • Cloud-Based Planning:

  • Planning and orchestration managed via Sonnet 5.5 on OpenRouter infrastructure

  • Simulation Setup:

  • Prompt: Single-line instruction initiating five physics scenarios displayed on a webpage:
    • Falling tower
    • Balls in a box
    • Wrecking ball
    • Seesaw
    • Bounce test
  • Each scenario executed autonomously, no human intervention or edits

Experimental Results

| Configuration | Scenes Completed | Processing Time | Cloud Cost |
|————————————————–|——————–|—————–|————|
| Qwen 3.8 27B alone | 1/5 | 26 minutes | $0 |
| Sonnet 5.5 plans; Qwen writes code | 2/5 | 85 minutes | ~$0.67 |
| Qwen plans; Sonnet 5.5 writes code | 4/5 | 14 minutes | ~$2.77 |
| Sonnet 5.5 alone | 4/5 | 9 minutes | ~$1.83 |

Key Insights and Observations

  • Planning vs. Coding Strengths:
    The Qwen model excels as a planner, matching Sonnet 5.5’s output quality when it devises scene instructions. However, as a code generator, it struggled with extensive physics code—producing hollow shells, hollowed-out cubes, and black blobs instead of accurate simulations. This emphasizes the model’s proficiency in strategic reasoning over detailed coding.

  • Hardware Performance:
    On the RTX 3090, the model achieved approximately 31–34 tokens/second during generation with meaningful prompt processing speeds (~1,080 tokens/second). A less capable GPU, like the RTX 3060 with 12 GB VRAM, proved insufficient—yielding only 4–6 tokens/second, with weights spilling into system RAM and hampering performance.

  • Model’s Thinking Behavior:
    Qwen tends to engage in intensive reasoning post-prompt. To prevent hang-ups or runaway processing, a reasoning budget cap was imposed. Without this safeguard, the model would often generate no output within 30 minutes, highlighting the importance of managing its computational effort.

  • Output Limitations:
    During code generation, Qwen occasionally attempted to produce very large files in a single reply (up to 16K tokens). When the output cap was reached, it necessitated reruns, underscoring the need for buffering or chunking in long code generation tasks.

  • Accuracy and Validation:
    Every run concluded with the message “verified, 0 errors,” and no runtime errors appeared in logs. Nonetheless, some scenes still displayed incorrect physics behavior—illustrating that crash checks and error reports may not fully capture underlying simulation inaccuracies.

Final Remarks

This hands-on exploration suggests that combining large language models like Qwen 3.8 27B with sophisticated planning tools such as Sonnet 5.5 presents a viable, resource-efficient approach to physics simulation tasks. The most notable advantage lies in reduced costs—approximately 2.7 times cheaper than solely cloud-based solutions—while maintaining acceptable quality.

It is vital to recognize that these observations stem from singular runs rather than comprehensive benchmarks, serving more as a field report of practical feasibility. For those interested, configuration details and logs can be shared upon request.

About the Project

This experiment was conducted within the Atomic Agent framework, an open-source project designed to facilitate autonomous AI agents using a modular fusion of planning and execution components. The project is available under the MIT license:

AtomicAgent on GitHub


In summary:
Leveraging locally hosted LLMs combined with intelligent planning can deliver substantial cost savings without significantly sacrificing performance. While some technical considerations remain—such as managing output size and model thinking budgets—this approach offers a promising pathway for deploying AI-driven physics simulations in a resource-conscious manner.

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