arXiv subjects

Kazem Cheshmi

Publications and source records attributed to Kazem Cheshmi.

9 recordsLinked to original sources

arXiv2026

ARASH: Adaptive Retrieval And Shot Selection for Tabular Prediction

Tabular prediction is a critical task across numerous applications. The recent success of large language models has sparked various approaches for adapting them to the tabular domain. A prevalent strategy involves training or fine-tuning specialized Tabular Foundation Models (TFMs) such as TabPFN. However, TFMs require substantial computational resources, and frequent model retraining is often impractical. In-context learning (ICL), specifically, few-shot prompting, offers a resource-efficient alternative to enhance performance. Yet, identifying the most relevant rows to serve as shots remains a challenge for tabular data. This paper introduces ARASH (Adaptive, query-specific Retrieval And Shot selection), a method that improves TFM efficiency by selecting optimal shots based on local neighborhood analysis within the training set. Our results demonstrate that ARASH reduces the prompt length and memory usage of TabPFN by 1261.5$\times$ and 2.56$\times$, respectively, while providing comparable accuracy.

cs.AI↗

arXiv2025

Floating-Point Data Transformation for Lossless Compression

Floating-point data is widely used across various domains. Depending on the required precision, each floating-point value can occupy several bytes. Lossless storage of this information is crucial due to its critical accuracy, as seen in applications such as medical imaging and language model weights. In these cases, data size is often significant, making lossless compression essential. Previous approaches either treat this data as raw byte streams for compression or fail to leverage all patterns within the dataset. However, because multiple bytes represent a single value and due to inherent patterns in floating-point representations, some of these bytes are correlated. To leverage this property, we propose a novel data transformation method called Typed Data Transformation (TDT) that groups related bytes together to improve compression. We implemented and tested our approach on various datasets across both CPU and GPU. TDT achieves a geometric mean compression ratio improvement of 1.16$\times$ over state-of-the-art compression tools such as zstd, while also improving both compression and decompression throughput by 1.18--3.79$\times$.

cs.DB↗

arXiv2025

A Novel Compiler Transformation for Fast Sparse Matrix Multiplication in GPUs

Sparse data structures are commonly used in neural networks to reduce the memory footprint. These data structures are compact but cause irregularities such as random memory accesses, which prevent efficient use of the memory hierarchy. GPUs are a common platform for machine learning practitioners, but running compact data structures on these devices often leads to slow-downs due to inefficient use of computing and memory resources. This paper proposes a new compiler transformation, enumerate-and-sparse-coarsen, that accelerates sparse matrix-matrix multiplication (SPMM) on GPU devices. The transformation increases data reuse in registers and caches while creating more balanced workloads for GPU computing resources. The transformation is tested on sparse neural networks in convolutional and transformer models. On an A100 GPU and across a columns of matrix B (bCols) in $ A \times B = C$ from range of 32 to 128, the transformation yields a geometric mean speedup of 1.84$\times$ to 2.27$\times$ compared to cuBLAS and cuSPARSE baselines, respectively.

cs.PL↗

arXiv2024

Improving Locality in Sparse and Dense Matrix Multiplications

Consecutive matrix multiplications are commonly used in graph neural networks and sparse linear solvers. These operations frequently access the same matrices for both reading and writing. While reusing these matrices improves data locality, it presents a challenge due to the irregular dependencies between iterations across the two multiplication operations. Existing fusion methods often introduce excessive synchronization overhead or overlapped computations with limited benefits. This paper proposes tile fusion, a runtime approach that fuses tiles of the two matrix-matrix multiplications, where at least one of the involved matrices is sparse. Tile fusion aims to improve data locality while providing sufficient workload for cores in shared-memory multi-core processors. For a pair of matrix-matrix multiplications, tile fusion outperforms unfused baseline and MKL implementations with a geometric mean speedup of 1.97$\times$ 1.64$\times$, respectively, on multi-core CPUs.

cs.DC↗

arXiv2021

Vectorizing Sparse Matrix Codes with Dependency Driven Trace Analysis

Sparse computations frequently appear in scientific simulations and the performance of these simulations rely heavily on the optimization of the sparse codes. The compact data structures and irregular computation patterns in sparse matrix computations introduce challenges to vectorizing these codes. Available approaches primarily vectorize regular regions of computations in the sparse code. They also reorganize data and computations, at a cost, to increase the number of regular regions. In this work, we propose a novel polyhedral model, called the partially strided codelets (PSC), that enables the vectorization of computation regions with irregular data access patterns. PSCs also improve data locality in sparse computation. Our DDF inspector-executor framework efficiently mines the memory accesses in the sparse computation, using an access function differentiation approach, to find PSC codelets. It generates vectorized code for the sparse matrix multiplication kernel (SpMV), a kernel with parallel outer loops, and for kernels with carried dependence, specifically the sparse triangular solver (SpTRSV). We demonstrate the performance of the DDF-generated code on a set of 60 large and small matrices (0.05-130M nonzeros). DDF outperforms the highly specialized library MKL with an average speedup of 1.93 and 4.5X for SpMV and SpTRSV, respectively. For the same matrices, DDF outperforms the state-of-the-art inspector-executor framework Sympiler [1] for the SpTRSV kernel by up to 11X and the work by Augustine et. al [2] for the SpMV kernel by up to 12X.

cs.PL↗

arXiv2021

Composing Loop-carried Dependence with Other Loops

Sparse fusion is a compile-time loop transformation and runtime scheduling implemented as a domain-specific code generator. Sparse fusion generates efficient parallel code for the combination of two sparse matrix kernels where at least one of the kernels has loop-carried dependencies. Available implementations optimize individual sparse kernels. When optimized separately, the irregular dependence patterns of sparse kernels create synchronization overheads and load imbalance, and their irregular memory access patterns result in inefficient cache usage, which reduces parallel efficiency. Sparse fusion uses a novel inspection strategy with code transformations to generate parallel fused code for sparse kernel combinations that is optimized for data locality and load balance. Code generated by Sparse fusion outperforms the existing implementations ParSy and MKL on average 1.6X and 5.1X respectively and outperforms the LBC and DAGP coarsening strategies applied to a fused data dependence graph on average 5.1X and 7.2X respectively for various kernel combinations.

cs.PL↗

arXiv2019

MatRox: Modular approach for improving data locality in Hierarchical (Mat)rix App(Rox)imation

Hierarchical matrix approximations have gained significant traction in the machine learning and scientific community as they exploit available low-rank structures in kernel methods to compress the kernel matrix. The resulting compressed matrix, HMatrix, is used to reduce the computational complexity of operations such as HMatrix-matrix multiplications with tuneable accuracy in an evaluation phase. Existing implementations of HMatrix evaluations do not preserve locality and often lead to unbalanced parallel execution with high synchronization. Also, current solutions require the compression phase to re-execute if the kernel method or the required accuracy change. In this work, we describe MatRox, a framework that uses novel structure analysis strategies, blocking and coarsen, with code specialization and a storage format to improve locality and create load-balanced parallel tasks for HMatrix-matrix multiplications. Modularization of the matrix compression phase enables the reuse of computations when there are changes to the input accuracy and the kernel function. The MatRox-generated code for matrix-matrix multiplication is 2.98x, 1.60x, and 5.98x faster than library implementations available in GOFMM, SMASH, and STRUMPACK respectively. Additionally, the ability to reuse portions of the compression computation for changes to the accuracy leads to up to 2.64x improvement with MatRox over five changes to accuracy using GOFMM.

cs.DC↗

arXiv2018

Sparse Matrix Code Dependence Analysis Simplification at Compile Time

Analyzing array-based computations to determine data dependences is useful for many applications including automatic parallelization, race detection, computation and communication overlap, verification, and shape analysis. For sparse matrix codes, array data dependence analysis is made more difficult by the use of index arrays that make it possible to store only the nonzero entries of the matrix (e.g., in A[B[i]], B is an index array). Here, dependence analysis is often stymied by such indirect array accesses due to the values of the index array not being available at compile time. Consequently, many dependences cannot be proven unsatisfiable or determined until runtime. Nonetheless, index arrays in sparse matrix codes often have properties such as monotonicity of index array elements that can be exploited to reduce the amount of runtime analysis needed. In this paper, we contribute a formulation of array data dependence analysis that includes encoding index array properties as universally quantified constraints. This makes it possible to leverage existing SMT solvers to determine whether such dependences are unsatisfiable and significantly reduces the number of dependences that require runtime analysis in a set of eight sparse matrix kernels. Another contribution is an algorithm for simplifying the remaining satisfiable data dependences by discovering equalities and/or subset relationships. These simplifications are essential to make a runtime-inspection-based approach feasible.

cs.PL↗

arXiv2017

Sympiler: Transforming Sparse Matrix Codes by Decoupling Symbolic Analysis

Sympiler is a domain-specific code generator that optimizes sparse matrix computations by decoupling the symbolic analysis phase from the numerical manipulation stage in sparse codes. The computation patterns in sparse numerical methods are guided by the input sparsity structure and the sparse algorithm itself. In many real-world simulations, the sparsity pattern changes little or not at all. Sympiler takes advantage of these properties to symbolically analyze sparse codes at compile-time and to apply inspector-guided transformations that enable applying low-level transformations to sparse codes. As a result, the Sympiler-generated code outperforms highly-optimized matrix factorization codes from commonly-used specialized libraries, obtaining average speedups over Eigen and CHOLMOD of 3.8X and 1.5X respectively.

cs.PL↗