Drive vs. Decay: On the Training Dynamics of Joint-Embedding Predictive Architectures
Organizations: Université Paris-Saclay, CNRS, CentraleSupélec, LISN, Orsay, France
Abstract
Joint-Embedding Predictive Architectures (JEPAs) are prone to representation collapse, typically mitigated through empirical heuristics. We develop an early-training stability theory that unifies these heuristics. Linearising the coupled JEPA gradient flow around the trivial fixed point reveals two competing effects: a driving force () and a decay effect (). Under approximate spectral decoupling, a per-mode stability ratio factorises into independent data-side and predictor-side terms and the count of unstable modes tracks the rank of representations that can emerge. The framework predicts a phase boundary, which we confirm empirically across more than 800 Tabular-JEPA configurations. It also unifies predictor scaling, masking ratio, and EMA as distinct mechanisms for shifting . Guided by this analysis, we introduce ResidualPred, a transformer predictor whose attention is biased toward the identity at initialisation; it improves both effective rank and downstream accuracy on tabular benchmarks and in I-JEPA pretraining on CIFAR-10, CIFAR-100, STL-10, and ImageNet. Our framework connects empirical collapse-avoidance heuristics to an explicit dynamical picture, yielding theory-driven stabilizers. Code is available at https://github.com/jose-melo/drive-vs-decay.
Figures & tables
| Model | Context ratio | Predictor scale | Epoch 0 | Last epoch | Final loss | Test Acc. | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Tabular–JEPA variants | low | low | ||||||||||
| medium | ||||||||||||
| high | ||||||||||||
| low | medium | |||||||||||
| medium | ||||||||||||
| Mechanism | Derived dose | Mode escapes iff |
|---|---|---|
| Weight decay | additive floor: | |
| SIGReg | lowers the predictor factor: | |
| VICReg hinge | lowers it by , its small-weight dose | |
| Mimetic initialisation | dosed once, washed out at rate | integrated growth clears |
| Identity predictor | fixed; a data-spectrum condition | , |
| Tabular brittle regime | Image | ||||||
|---|---|---|---|---|---|---|---|
| Variant | Jannis | Helena | Variant | CIFAR-10 | CIFAR-100 | STL-10 | IN-100 |
| T-JEPA | I-JEPA | ||||||
| + ResPred | + ResPred | ||||||
| Linear (%) | Effective rank | |
|---|---|---|
| I-JEPA | ||
| + SIGReg | ||
| + ResPred | ||
| + ResPred + SIGReg |
Appendix figures & tables27 assets
Supplementary material from the paper’s appendix.
Appendix
| at | ||
|---|---|---|
| isotropic ( ) | ||
| diagonal power-law | ||
| CIFAR-10 raw patches ( , ) | ||
| synthetic rotated power-law | ||
| synthetic strong rank-decay |
| aloi ( ) | helena ( ) | jannis ( ) | |
|---|---|---|---|
| (abs., Cor. 3.3 ) | |||
| (abs.) | |||
| (signed) | |||
| (signed) | |||
| (scalar) |
| 100 epochs | 300 epochs | |||
|---|---|---|---|---|
| Variant | Acc. (%) | / vs Std | Acc. (%) | / vs Std |
| Standard | – | – | ||
| ZeroInit only | / | / | ||
| ResidualPred (bias only) | / | / | ||
| ResidualPred ZeroInit | / | / | ||
| Library | Description |
|---|---|
| Python v3.12 | Core programming language used for all experiments |
| pytorch 2.0.0 | Deep learning framework used to implement all models |
| numpy 1.24.0 | Numerical computing and array operations |
| sciPy 1.10.0 | Scientific computing utilities and linear algebra |
| pandas 2.0.0 | Tabular data processing and experiment management |
| scikit-learn 1.2.0 | Baseline models and evaluation utilities |
| Jannis | Helena | ALOI | |
| Samples | 83,733 | 65,196 | 108,000 |
| Numerical | |||
| Classes | |||
| Metric | Accuracy | Accuracy | Accuracy |
| Dataset | Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SEM | Mean | SEM | Mean | SEM | Mean | SEM | ||||||
| ALOI | 0.2 | 0.01 | 0 | ||||||||||
| Helena | 0.2 | 0.01 | 0 | ||||||||||
| Jannis | 0.2 | 0.01 | 0 | ||||||||||
| ALOI | 0.2 | 0.05 | 1 | ||||||||||
| Helena | 0.2 | 0.05 | 1 | ||||||||||
| Dataset | Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SEM | Mean | SEM | Mean | SEM | Mean | SEM | ||||||
| ALOI | 0.2 | 0.50 | 5 | ||||||||||
| Helena | 0.2 | 0.50 | 5 | ||||||||||
| Jannis | 0.2 | 0.50 | 5 | ||||||||||
| ALOI | 0.2 | 1.00 | 6 | ||||||||||
| Helena | 0.2 | 1.00 | 6 | ||||||||||
| Dataset | Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SEM | Mean | SEM | Mean | SEM | Mean | SEM | ||||||
| ALOI | 0.3 | 0.20 | 10 | ||||||||||
| Helena | 0.3 | 0.20 | 10 | ||||||||||
| Jannis | 0.3 | 0.20 | 10 | ||||||||||
| ALOI | 0.3 | 0.30 | 11 | ||||||||||
| Helena | 0.3 | 0.30 | 11 | ||||||||||
| Dataset | Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SEM | Mean | SEM | Mean | SEM | Mean | SEM | ||||||
| ALOI | 0.4 | 0.20 | 17 | ||||||||||
| Helena | 0.4 | 0.20 | 17 | ||||||||||
| Jannis | 0.4 | 0.20 | 17 | ||||||||||
| ALOI | 0.4 | 0.30 | 18 | ||||||||||
| Helena | 0.4 | 0.30 | 18 | ||||||||||
| Dataset | Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean | SEM | Mean | SEM | Mean | SEM | Mean | SEM | ||||||
| ALOI | 0.7 | 0.01 | 35 | ||||||||||
| Helena | 0.7 | 0.01 | 35 | ||||||||||
| Jannis | 0.7 | 0.01 | 35 | ||||||||||
| ALOI | 0.7 | 0.05 | 36 | ||||||||||
| Helena | 0.7 | 0.05 | 36 | ||||||||||
| Context | Predictor scale | Config ID | Epoch 0 | Epoch 0 Erank | Last epoch | Last epoch Erank | Final loss | Test Acc. |
|---|---|---|---|---|---|---|---|---|
| Variant | Dataset | Seed | ERank 0 | ERank last | Final loss | Probe acc. (%) | ||
| Standard | jannis | |||||||
| Standard | jannis | |||||||
| Standard | jannis | |||||||
| Standard | jannis | |||||||
| Standard | jannis | |||||||
| Standard | jannis |
| Variant | Dataset | ERank last | Final loss | Probe acc. (%) | |||||
|---|---|---|---|---|---|---|---|---|---|
| Mean | Std | Mean | Std | Mean | Std | ||||
| Standard | jannis | ||||||||
| Standard | jannis | ||||||||
| Standard | jannis | ||||||||
| Standard | helena | ||||||||
| Standard | helena | ||||||||
| Dataset | Variant | Seed | ERank 0 | ERank 100 | Probe (%) | |
|---|---|---|---|---|---|---|
| CIFAR-10 | Standard | |||||
| CIFAR-10 | Standard | |||||
| CIFAR-10 | Standard | |||||
| CIFAR-10 | +ResPred | |||||
| CIFAR-10 | +ResPred | |||||
| CIFAR-10 | +ResPred |
| Dataset | Variant | ERank 0 | ERank 100 | Probe (%) | ||||
|---|---|---|---|---|---|---|---|---|
| Mean | Std | Mean | Std | Mean | Std | |||
| CIFAR-10 | Standard | |||||||
| CIFAR-10 | +ResPred | |||||||
| CIFAR-100 | Standard | |||||||
| CIFAR-100 | +ResPred | |||||||
| STL-10 | Standard | |||||||
| Readout | Depth 2 | Depth 6 |
|---|---|---|
| Linear probe | pp | pp |
| Nearest neighbour, | pp | pp |
| Attentive probe | pp | pp |
| Effective rank | ( ) |
| Readout at epoch 30 | Standard | ResidualPred | |
|---|---|---|---|
| Linear probe | pp | ||
| Nearest neighbour, | pp | ||
| Attentive probe | pp | ||
| Effective rank |
| Setting | Standard | ResidualPred | |
|---|---|---|---|
| pixels, epochs | ( to ) | ( to ) | pp |
| pixels, epochs | ( to ) | ( to ) | pp |
| Predictor and loss | Linear | Range | Nearest neighbour | Attentive | Effective rank | |
|---|---|---|---|---|---|---|
| Standard | 5 | to | ||||
| Standard SIGReg, | 2 | to | to | |||
| Standard SIGReg, (default) | 7 | to | to | |||
| Standard SIGReg, | 2 | to | to | |||
| ResidualPred , | 5 | to | ||||
| ResidualPred SIGReg, | 5 | to | to |
| Mechanism | Derived effect on | Predicted vs measured |
|---|---|---|
| Weight decay on the encoder | Raises every mode’s decay by : escape iff . | Five doses, three seeds ( runs); predicted counts , matched in every run. |
| Predictor scaling (Mechanism 1) | ; nothing escapes above . | ladder bracketing , three seeds ( runs); count exact in every run. |
| SIGReg [ Balestriero and LeCun, 2025 ] | Lowers the decay’s predictor factor by : escape iff . | Fifteen doses, three seeds ( runs), plus six teacher-free doses ( ); counts to and , exact in every run. |
| VICReg hinge [ Bardes et al., 2022 ] | Lowers the decay’s predictor factor by for a mode of standard deviation ; rescue dose . | Four doses, three seeds ( runs); of exact. |
| Mimetic initialisation [ Trockman and Kolter, 2023 ] | Doses the alignment ratio once, washed out at rate . | Eight wash-out rates, three seeds ( runs); of exact. |
| Identity predictor | With frozen, mode escapes iff . | Four configurations plus a BYOL-style setting, three seeds ( runs); and , exact. |