Implicit Dynamical Flow Fusion (IDFF) for Generative Modeling
Mohammad R. Rezaei, Milos R. Popovic, Milad Lankarany, Rahul G. Krishnan

TL;DR
IDFF introduces a new vector field with momentum for generative modeling, significantly reducing network evaluations needed for high-quality sample generation across images and time-series data.
Contribution
It proposes Implicit Dynamical Flow Fusion (IDFF), a novel method that accelerates sample generation by enabling longer steps while maintaining fidelity, reducing NFEs by tenfold.
Findings
Achieves comparable likelihood and quality to existing models with fewer NFEs
Reduces sampling time significantly without loss of fidelity
Demonstrates versatility across image and time-series datasets
Abstract
Conditional Flow Matching (CFM) models can generate high-quality samples from a non-informative prior, but they can be slow, often needing hundreds of network evaluations (NFE). To address this, we propose Implicit Dynamical Flow Fusion (IDFF); IDFF learns a new vector field with an additional momentum term that enables taking longer steps during sample generation while maintaining the fidelity of the generated distribution. Consequently, IDFFs reduce the NFEs by a factor of ten (relative to CFMs) without sacrificing sample quality, enabling rapid sampling and efficient handling of image and time-series data generation tasks. We evaluate IDFF on standard benchmarks such as CIFAR-10 and CelebA for image generation, where we achieve likelihood and quality performance comparable to CFMs and diffusion-based models with fewer NFEs. IDFF also shows superior performance on time-series datasets…
Peer Reviews
Decision·Submitted to ICLR 2025
1. The authors present a new objective for training and sampling in CFMs that combines some aspects of stochasticity of score-based, making the NFEs lower at inference and improving sample generation quality. 2. The authors have provided thorough proof of the derivations for the formulation. 3. The authors have not only shown that their method performs better in image generation but also that it can be used in tasks of other domains like time series.
1. Figure 2 C) is a bit confusing by itself. Only after reading Algorithm 2 was the figure easy to understand. The authors can try to make the figure self-sufficient in understandability. 2. The authors compare image generation quality w.r.t sampling strategies like DDIM and DPM and show that their model achieves the best quality. 3. However, they have not compared against better strategies like EDM. A comparison against EDM would be even more insightful. How does the method proposed by authors
The paper tackles the important problem of reducing NFE in sampling process of flow/bridge models. The method is compared on number of different domians.
1. The proposed loss seems similar to the loss proposed in [2] for simulation free training of Schrödinger bridges up to parametrizing the the velocity field with a denoiser. 2. In the CIFAR10 experiment the author chose to compare to DPM-solver [3] only, while there are already two follow up works DPM++ [4] and DPM-v3-solver [5] which in [5] are reported to perform better than the proposed IDFF method. Additionally, Uni-PC solver [6] is reported to perform better. 3. of less importance but I
1. The idea presented is novel and effective, as demonstrated by the experiments. 2. The proofs provided in this paper are solid. 3. This paper also discusses the topic of time-series generation.
I believe the main drawback is that I cannot find an explanation for how this momentum term helps reduce the NFE. It appears that the motivation for designing this method is inspired by Hamiltonian Monte Carlo, which, by the way, is not mentioned in the background section. If I have overlooked this part, please let me know. If not, I recommend adding an explanation. If it is well justified, I will reconsider my score. Here are some specific suggestions. 1. It would be beneficial to include a di
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Taxonomy
TopicsSimulation Techniques and Applications
MethodsDiffusion
