arXiv subjects

Langwen Huang

Publications and source records attributed to Langwen Huang.

8 recordsLinked to original sources

arXiv2026

Scaling Laws of Global Weather Models

Data-driven models are revolutionizing weather forecasting. To optimize training efficiency and model performance, this paper analyzes empirical scaling laws within this domain. We investigate the relationship between model performance (validation loss) and three key factors: model size ($N$), dataset size ($D$), and compute budget ($C$). Across a range of models, we find that Aurora exhibits the strongest data-scaling behavior: increasing the training dataset by 10x reduces validation loss by up to 3.2x. GraphCast demonstrates the highest parameter efficiency, yet suffers from limited hardware utilization. Our compute-optimal analysis indicates that, under fixed compute budgets, allocating resources to more total training data yields greater performance gains than increasing model size. Furthermore, we analyze model shape and uncover scaling behaviors that differ fundamentally from those observed in language models: weather forecasting models consistently favor increased width over depth. These findings suggest that future weather models should prioritize wider architectures and larger effective training datasets to maximize predictive performance.

cs.LG↗

arXiv2026

Error bounded compression for weather and climate applications

As the resolution of weather and climate simulations increases, the amount of data produced is growing rapidly from hundreds of terabytes to tens of petabytes. The huge size becomes a limiting factor for broader adoption, and its fast growth rate will soon exhaust all the available storage devices. To address these issues, we present EBCC (Error Bounded Climate-data Compressor). It follows a two-layer approach: a base compression layer using JPEG2000 to capture the bulk of the data with a high compression ratio, and a residual compression layer using wavelet transform and SPIHT encoding to efficiently eliminate long-tail extreme errors introduced by the base compression layer. It incorporates a feedback rate-control mechanism for both layers that adjusts compression ratios to achieve the specified maximum error target. We evaluate EBCC alongside other established compression methods on benchmarks related to weather and climate science including error statistics, a case study on primitive and derived variables near a hurricane, evaluation of the closure of the global energy budget, and a Lagrangian air parcel trajectory simulation. This is the first time that trajectory simulation is used to benchmark compression methods. Our method concentrates most errors near zero, while others tend to distribute errors uniformly within the error bound. EBCC outperforms other methods in the benchmarks at relative error targets ranging from 0.1% to 10% and achieves compression ratios from 15x to more than 300x. In the energy budget closure and Lagrangian trajectory benchmarks, it can achieve more than 100x compression while keeping errors within natural variability derived from ERA5 uncertainty members. This verifies the effectiveness of EBCC in creating heavily compressed weather and climate datasets suitable for downstream applications. The source code of EBCC is available in github.com/spcl/EBCC.

cs.CE↗

arXiv2025

CrossPipe: Towards Optimal Pipeline Schedules for Cross-Datacenter Training

Training large language models (LLMs) now requires resources that exceed a single datacenter, making cross-datacenter strategies increasingly crucial. We present CrossPipe, a framework designed to optimize model training across geographically distributed datacenters by explicitly modeling and mitigating the impact of network latency and limited bandwidth. It enables unified analysis and optimization incorporating both pipeline parallelism (PP) and opportunities for overlapping data parallelism (DP) communication. CrossPipe generates optimized pipeline schedules using either solver-based optimal or fast near-optimal greedy algorithms, built upon a flexible execution engine that separates scheduling logic from communication details. Our evaluation shows that CrossPipe reduces training time by up to 33.6\% compared to traditional pipeline schedules under identical memory constraints. When memory constraints are relaxed, CrossPipe maintains strong performance despite communication delays, approaching the efficiency of idealized schedules without delays. CrossPipe offers improved scalability and resource utilization, particularly in environments with high network latency or limited bandwidth.

cs.DC↗

arXiv2024

DiffDA: a Diffusion Model for Weather-scale Data Assimilation

The generation of initial conditions via accurate data assimilation is crucial for weather forecasting and climate modeling. We propose DiffDA as a denoising diffusion model capable of assimilating atmospheric variables using predicted states and sparse observations. Acknowledging the similarity between a weather forecast model and a denoising diffusion model dedicated to weather applications, we adapt the pretrained GraphCast neural network as the backbone of the diffusion model. Through experiments based on simulated observations from the ERA5 reanalysis dataset, our method can produce assimilated global atmospheric data consistent with observations at 0.25 deg (~30km) resolution globally. This marks the highest resolution achieved by ML data assimilation models. The experiments also show that the initial conditions assimilated from sparse observations (less than 0.96% of gridded data) and 48-hour forecast can be used for forecast models with a loss of lead time of at most 24 hours compared to initial conditions from state-of-the-art data assimilation in ERA5. This enables the application of the method to real-world applications, such as creating reanalysis datasets with autoregressive data assimilation.

cs.CE↗

arXiv2024

LLAMP: Assessing Network Latency Tolerance of HPC Applications with Linear Programming

The shift towards high-bandwidth networks driven by AI workloads in data centers and HPC clusters has unintentionally aggravated network latency, adversely affecting the performance of communication-intensive HPC applications. As large-scale MPI applications often exhibit significant differences in their network latency tolerance, it is crucial to accurately determine the extent of network latency an application can withstand without significant performance degradation. Current approaches to assessing this metric often rely on specialized hardware or network simulators, which can be inflexible and time-consuming. In response, we introduce LLAMP, a novel toolchain that offers an efficient, analytical approach to evaluating HPC applications' network latency tolerance using the LogGPS model and linear programming. LLAMP equips software developers and network architects with essential insights for optimizing HPC infrastructures and strategically deploying applications to minimize latency impacts. Through our validation on a variety of MPI applications like MILC, LULESH, and LAMMPS, we demonstrate our tool's high accuracy, with relative prediction errors generally below 2%. Additionally, we include a case study of the ICON weather and climate model to illustrate LLAMP's broad applicability in evaluating collective algorithms and network topologies.

cs.DC↗

arXiv2024

Arrow Matrix Decomposition: A Novel Approach for Communication-Efficient Sparse Matrix Multiplication

We propose a novel approach to iterated sparse matrix dense matrix multiplication, a fundamental computational kernel in scientific computing and graph neural network training. In cases where matrix sizes exceed the memory of a single compute node, data transfer becomes a bottleneck. An approach based on dense matrix multiplication algorithms leads to suboptimal scalability and fails to exploit the sparsity in the problem. To address these challenges, we propose decomposing the sparse matrix into a small number of highly structured matrices called arrow matrices, which are connected by permutations. Our approach enables communication-avoiding multiplications, achieving a polynomial reduction in communication volume per iteration for matrices corresponding to planar graphs and other minor-excluded families of graphs. Our evaluation demonstrates that our approach outperforms a state-of-the-art method for sparse matrix multiplication on matrices with hundreds of millions of rows, offering near-linear strong and weak scaling.

cs.DC↗

arXiv2023

Compressing multidimensional weather and climate data into neural networks

Weather and climate simulations produce petabytes of high-resolution data that are later analyzed by researchers in order to understand climate change or severe weather. We propose a new method of compressing this multidimensional weather and climate data: a coordinate-based neural network is trained to overfit the data, and the resulting parameters are taken as a compact representation of the original grid-based data. While compression ratios range from 300x to more than 3,000x, our method outperforms the state-of-the-art compressor SZ3 in terms of weighted RMSE, MAE. It can faithfully preserve important large scale atmosphere structures and does not introduce artifacts. When using the resulting neural network as a 790x compressed dataloader to train the WeatherBench forecasting model, its RMSE increases by less than 2%. The three orders of magnitude compression democratizes access to high-resolution climate data and enables numerous new research directions.

cs.LG↗

arXiv2022

ENS-10: A Dataset For Post-Processing Ensemble Weather Forecasts

Post-processing ensemble prediction systems can improve the reliability of weather forecasting, especially for extreme event prediction. In recent years, different machine learning models have been developed to improve the quality of weather post-processing. However, these models require a comprehensive dataset of weather simulations to produce high-accuracy results, which comes at a high computational cost to generate. This paper introduces the ENS-10 dataset, consisting of ten ensemble members spanning 20 years (1998-2017). The ensemble members are generated by perturbing numerical weather simulations to capture the chaotic behavior of the Earth. To represent the three-dimensional state of the atmosphere, ENS-10 provides the most relevant atmospheric variables at 11 distinct pressure levels and the surface at 0.5-degree resolution for forecast lead times T=0, 24, and 48 hours (two data points per week). We propose the ENS-10 prediction correction task for improving the forecast quality at a 48-hour lead time through ensemble post-processing. We provide a set of baselines and compare their skill at correcting the predictions of three important atmospheric variables. Moreover, we measure the baselines' skill at improving predictions of extreme weather events using our dataset. The ENS-10 dataset is available under the Creative Commons Attribution 4.0 International (CC BY 4.0) license.

cs.LG↗