Davide Barbieri

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In this paper we develop a geometrical model of functional architecture for the processing of spatio-temporal visual stimuli. The model arises from the properties of the receptive field linear dynamics of orientation and speed-selective cells in the visual cortex, that can be embedded in the definition of a geometry where the connectivity between points is(More)
We present a model of the morphology of orientation maps in V1 based on the uncertainty principle of the SE(2) group. Starting from the symmetries of the cortex, suitable harmonic analysis instruments are used to obtain coherent states in the Fourier domain as minimizers of the uncertainty. Cortical activities related to orientation maps are then obtained(More)
In recent literature, particularly interesting stimulus velocity-selective behaviors were found in the response properties of neurons belonging to the primary visual cortex (V1). In this work, 93 simple and complex cell receptive fields were obtained from the recordings of different experiments made on cats (DeAngelis, Blanche, Touryan) with reverse(More)
General purpose computing on graphics processing units (GPGPU) is fast becoming a common feature of high performance computing centers. In this paper we discuss some implementation issues related to dense linear algebra computations on GPUs, such as the GEneral Matrix-Matrix product, as well as other kernels sharing the same computational pattern, such as(More)
We discuss object-oriented software design patterns in the context of scientific computations on sparse matrices. Design patterns arise when multiple independent development efforts produce very similar designs, yielding an evolutionary convergence onto a good solution: a flexible, maintainable, high-performance design. We demonstrate how to engender these(More)
The visual systems of many mammals, including humans, are able to integrate the geometric information of visual stimuli and perform cognitive tasks at the first stages of the cortical processing. This is thought to be the result of a combination of mechanisms, which include feature extraction at the single cell level and geometric processing by means of(More)
Domain decomposition based on spatial locality is a classical data-parallel problem whose solution may improve by orders of magnitude when implemented on a GPU. Among the data structures involved in domain decomposition, uniform grids are widely used to speed up simulations in a number of fields, including computational physics and graphics. In this work,(More)
—In this paper we study the long-term throughput performance of repetition protocols coupled with power control for multiple access block-fading channels. We propose to use the feedback bits to inform the transmitter about the decoding status and the instantaneous channel quality. We determine the throughput of simple and practically inspired protocols; we(More)
—Exhaustive search is generally a last resort for solving a problem: each possible state of a system is generated and evaluated against a condition to find if the problem solution is attained. In some cases, for example in the reversal of cryptographic hash functions that make use of the salting technique, there are very few valid alternatives. However, the(More)
Increased sedentary lifestyle and prevalence of overweight/obesity are common in western countries. The purposes of this study were (i) to assess the main health-related anthropometric characteristics in a sample of students in relation to sex, amount of physical activity and sport discipline, and (ii) to investigate the accuracy of the Body Mass Index(More)