Estimating GPT-3 Training FLOPs

I'll estimate the total number of floating point operations (FLOPs) required to train GPT-3 by breaking down the calculation step by step.

Model Architecture Facts

• GPT-3 has approximately 175 billion parameters
• Uses a transformer architecture with multiple layers
• Context length of 2048 tokens
• Trained on approximately 300 billion tokens

Calculating FLOPs per Token

For transformer models, we need to account for operations in:

1. Self-attention mechanisms
2. Feed-forward networks
3. Layer normalization and other operations

For GPT-3, let's use these parameters:

• Embedding dimension (d): ~12,288
• Number of layers (L): ~96
• Context length (s): 2,048

Forward Pass Calculation

For each token in each layer:

• Self-attention: ~4 × d² + 2 × d × s FLOPs
• Feed-forward network: ~8 × d² FLOPs
• Other operations: ~d FLOPs

Total FLOPs per token (forward pass): ≈ L × (12 × d² + 2 × d × s) ≈ 96 × (12 × 12,288² + 2 × 12,288 × 2,048) ≈ 96 × (1.8 × 10⁹ + 5 × 10⁷) ≈ 1.8 × 10¹¹ FLOPs

Backward Pass

The backward pass typically requires about 2× the computation of the forward pass: ≈ 2 × 1.8 × 10¹¹ ≈ 3.6 × 10¹¹ FLOPs

Total FLOPs per token (forward + backward): ≈ 1.8 × 10¹¹ + 3.6 × 10¹¹ ≈ 5.4 × 10¹¹ FLOPs

Total Training FLOPs

Multiply by the total number of tokens processed: ≈ 5.4 × 10¹¹ × 300 × 10⁹ ≈ 1.62 × 10²³ FLOPs

Alternative Calculation

As a sanity check, using a simpler heuristic:

• Each parameter requires ~2-4 FLOPs per token (including forward, backward, and weight update)
• 175B parameters × 4 FLOPs × 300B tokens ≈ 2.1 × 10²³ FLOPs

Conclusion

The total training computation for GPT-3 was approximately 1.6-2.1 × 10²³ FLOPs (160-210 zettaFLOPs).

This massive computational requirement explains why training such models costs millions of dollars and requires specialized supercomputing infrastructure.