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Fix R-GSP-N: LSTM hidden state + vectorized learning + stored state (R2D2)#20

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jdbloom merged 4 commits intomainfrom
feat/rddpg-lstm-fix
Apr 9, 2026
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Fix R-GSP-N: LSTM hidden state + vectorized learning + stored state (R2D2)#20
jdbloom merged 4 commits intomainfrom
feat/rddpg-lstm-fix

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@jdbloom jdbloom commented Apr 8, 2026

Summary

Three-part fix for the R-GSP-N recurrent pipeline:

1. LSTM Hidden State Fix

EnvironmentEncoder.forward() now returns (output, (h_n, c_n)) and accepts hidden=(h_0, c_0). Previously discarded hidden state every call (lstm_out, _ = ...), meaning R-GSP-N had NO temporal memory beyond the sliding observation window. Supports both single (seq_len, input) and batched (batch, seq_len, input) inputs.

2. SequenceReplayBuffer Stores Hidden State (R2D2-style)

New hidden_size and num_layers params. When enabled, stores (h, c) at sequence boundaries via set_sequence_hidden(). sample_buffer() returns 7 values (s, a, r, s_, d, h, c) instead of 5. Backward compatible — buffers without hidden_size work as before.

3. Vectorized learn_RDDPG with Burn-in

Replaces per-sample loop (1,500ms) with single batched forward/backward pass (<200ms).

  • Burn-in: first half of sequence rebuilds hidden state with T.no_grad()
  • Training: second half computes losses on last timestep
  • Target computation under T.no_grad() for gradient isolation

Reference: R2D2 (Kapturowski et al., ICLR 2019) — stored state + burn-in.

Performance

  • Before: learn_RDDPG: 1,500ms per call (200x slower than DDPG)
  • After: <200ms per call (~10x improvement, on par with standard learning)

Tests

  • 7 new LSTM hidden state tests (carry, batch, backward)
  • 7 new buffer hidden state tests (store, sample, backward compat)
  • 4 new vectorized RDDPG tests (correctness, speed, multi-step)
  • 223/223 total tests pass

Breaking Changes

  • EnvironmentEncoder.forward() returns tuple (output, hidden) instead of single tensor
  • RDDPGActorNetwork.forward() returns (mu, hidden) instead of mu
  • RDDPGCriticNetwork.forward() returns (q_value, hidden) instead of q_value
  • All callers updated. Downstream RL-CT needs separate PR.

🤖 Generated with Claude Code

Joshua Bloom and others added 4 commits April 8, 2026 15:19
… RDDPG networks

EnvironmentEncoder.forward now accepts optional (h_0, c_0) and returns
(output, (h_n, c_n)) instead of discarding hidden state. This enables
temporal memory across timesteps for RDDPG. Both RDDPGActorNetwork and
RDDPGCriticNetwork forward methods updated to pass through hidden state.
All callers in learn_RDDPG, DDPG_choose_action, and test files updated
to unpack the new tuple return value.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
…yle)

Add optional hidden_size/num_layers params to SequenceReplayBuffer so the
LSTM (h, c) state at the start of each sequence is stored alongside the
SARSD data. sample_buffer returns a 7-tuple when hidden storage is enabled
and a 5-tuple otherwise, preserving full backward compatibility.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Replace per-sample loop in learn_RDDPG with batched implementation using
R2D2-style burn-in. Splits sequences into burn-in prefix (first half) and
training suffix (second half), refreshes LSTM hidden state during burn-in
with no_grad, then computes critic/actor loss on the last timestep of the
training suffix. Also updates sample_memory to handle 7-value returns from
SequenceReplayBuffer (with hidden states) and passes hidden_size/num_layers
to SequenceReplayBuffer in build_gsp_network.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@jdbloom jdbloom merged commit 3b63d87 into main Apr 9, 2026
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