Method for dynamic power monitoring on FPGAs

International audienceThe ever-increasing integration densities make it possible to configure multi-core systems composed of hundreds of blocks on existing FPGAs that may influence overall consumption differently. Observing total consumption is not sufficient to accurately assess internal circuit activity to be able to deploy effective adaptation strategies. In this case monitoring techniques are required. This paper presents a CAD flow for high-level dynamic power estimation on FPGAs. The method is based on the monitoring of toggling activity for relevant signals by introducing event counters. The appropriate signals are selected using the Greedy Stepwise filter. Our approach is based on a generic method that is able to produce a power model for any block-based circuit. We evaluated our contribution on a SoC RTL model implemented on Spartan3, Virtex5, and Spartan6 FPGAs. A power model and monitors are automatically generated to achieve the best tradeoff between accuracy and overhead

On Ziv's rounding test

International audienceA very simple test, introduced by Ziv, allows one to determine if an approximation to the value f (x) of an elementary function at a given point x suffices to return the floating-point number nearest f(x). The same test may be used when implementing floating-point operations with input and output operands of different formats, using arithmetic operators tailored for manipulating operands of the same format. That test depends on a "magic constant" e. We show how to choose that constant e to make the test reliable and efficient. Various cases are considered, depending on the availability of an fma instruction, and on the range of f (x)

SymTrees and Multi-Sector QFTs

The global symmetries of a $D$-dimensional QFT can, in many cases, be captured in terms of a $(D+1)$-dimensional symmetry topological field theory (SymTFT). In this work we construct a $(D+1)$-dimensional theory which governs the symmetries of QFTs with multiple sectors which have connected correlators that admit a decoupling limit. The associated symmetry field theory decomposes into a SymTree, namely a treelike structure of SymTFTs fused along possibly non-topological junctions. In string-realized multi-sector QFTs, these junctions are smoothed out in the extra-dimensional geometry, as we demonstrate in examples. We further use this perspective to study the fate of higher-form symmetries in the context of holographic large $M$ averaging where the topological sectors of different large $M$ replicas become dressed by additional extended operators associated with the SymTree.Comment: 69 pages + appendices + ref

Loop Optimization in Presence of STT-MRAM Caches: a Study of Performance-Energy Tradeoffs

International audienceEnergy-efficiency is one of the most challenging design issues in both embedded and high-performance computing domains. The aim is to reduce as much as possible the energy consumption of considered systems while providing them with the best computing performance. Finding an adequate solution to this problem certainly requires a cross-disciplinary approach capable of addressing the energy/performance trade-off at different system design levels. In this paper, we present an empirical impact analysis of the integration of Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) technologies in multicore architectures when applying some existing compiler optimizations. For that purpose, we use three well-established architecture and NVM evaluation tools: NVSim, gem5 and McPAT. Our results show that the integration of STT-MRAM at cache memory levels enables a significant reduction of the energy consumption (up to 24.2 % and 31 % on the considered multicore and monocore platforms respectively) while preserving the performance improvement provided by typical code optimizations. We also identify how the choice of the clock frequency impacts the relative efficiency of the considered memory technologies

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum