97,506 research outputs found
Inherently workload-balanced clustered microarchitecture
The performance of clustered microarchitectures relies on steering schemes that try to find the best trade-off between workload balance and inter-cluster communication penalties. In previously proposed clustered processors, reducing communication penalties and balancing the workload are opposite targets, since improving one usually implies a detriment in the other. In this paper we propose a new clustered microarchitecture that can minimize communication penalties without compromising workload balance. The key idea is to arrange the clusters in a ring topology in such a way that results of one cluster can be forwarded to the neighbor cluster with a very short latency. In this way, minimizing communication penalties is favored when the producer of a value and its consumer are placed in adjacent clusters, which also favors workload balance. The proposed microarchitecture is shown to outperform a state-of-the-art clustered processor. For instance, for an 8-cluster configuration and just one fully pipelined unidirectional bus, 15% speedup is achieved on average for FP programs.Peer ReviewedPostprint (published version
GLB: Lifeline-based Global Load Balancing library in X10
We present GLB, a programming model and an associated implementation that can
handle a wide range of irregular paral- lel programming problems running over
large-scale distributed systems. GLB is applicable both to problems that are
easily load-balanced via static scheduling and to problems that are hard to
statically load balance. GLB hides the intricate syn- chronizations (e.g.,
inter-node communication, initialization and startup, load balancing,
termination and result collection) from the users. GLB internally uses a
version of the lifeline graph based work-stealing algorithm proposed by
Saraswat et al. Users of GLB are simply required to write several pieces of
sequential code that comply with the GLB interface. GLB then schedules and
orchestrates the parallel execution of the code correctly and efficiently at
scale. We have applied GLB to two representative benchmarks: Betweenness
Centrality (BC) and Unbalanced Tree Search (UTS). Among them, BC can be
statically load-balanced whereas UTS cannot. In either case, GLB scales well--
achieving nearly linear speedup on different computer architectures (Power,
Blue Gene/Q, and K) -- up to 16K cores
Packet Transactions: High-level Programming for Line-Rate Switches
Many algorithms for congestion control, scheduling, network measurement,
active queue management, security, and load balancing require custom processing
of packets as they traverse the data plane of a network switch. To run at line
rate, these data-plane algorithms must be in hardware. With today's switch
hardware, algorithms cannot be changed, nor new algorithms installed, after a
switch has been built.
This paper shows how to program data-plane algorithms in a high-level
language and compile those programs into low-level microcode that can run on
emerging programmable line-rate switching chipsets. The key challenge is that
these algorithms create and modify algorithmic state. The key idea to achieve
line-rate programmability for stateful algorithms is the notion of a packet
transaction : a sequential code block that is atomic and isolated from other
such code blocks. We have developed this idea in Domino, a C-like imperative
language to express data-plane algorithms. We show with many examples that
Domino provides a convenient and natural way to express sophisticated
data-plane algorithms, and show that these algorithms can be run at line rate
with modest estimated die-area overhead.Comment: 16 page
Average treatment effect estimation via random recursive partitioning
A new matching method is proposed for the estimation of the average treatment
effect of social policy interventions (e.g., training programs or health care
measures). Given an outcome variable, a treatment and a set of pre-treatment
covariates, the method is based on the examination of random recursive
partitions of the space of covariates using regression trees. A regression tree
is grown either on the treated or on the untreated individuals {\it only} using
as response variable a random permutation of the indexes 1... ( being the
number of units involved), while the indexes for the other group are predicted
using this tree. The procedure is replicated in order to rule out the effect of
specific permutations. The average treatment effect is estimated in each tree
by matching treated and untreated in the same terminal nodes. The final
estimator of the average treatment effect is obtained by averaging on all the
trees grown. The method does not require any specific model assumption apart
from the tree's complexity, which does not affect the estimator though. We show
that this method is either an instrument to check whether two samples can be
matched (by any method) and, when this is feasible, to obtain reliable
estimates of the average treatment effect. We further propose a graphical tool
to inspect the quality of the match. The method has been applied to the
National Supported Work Demonstration data, previously analyzed by Lalonde
(1986) and others
Compression by Contracting Straight-Line Programs
In grammar-based compression a string is represented by a context-free
grammar, also called a straight-line program (SLP), that generates only that
string. We refine a recent balancing result stating that one can transform an
SLP of size in linear time into an equivalent SLP of size so that
the height of the unique derivation tree is where is the length
of the represented string (FOCS 2019). We introduce a new class of balanced
SLPs, called contracting SLPs, where for every rule the string length of every variable on the right-hand side
is smaller by a constant factor than the string length of . In particular,
the derivation tree of a contracting SLP has the property that every subtree
has logarithmic height in its leaf size. We show that a given SLP of size
can be transformed in linear time into an equivalent contracting SLP of size
with rules of constant length.
We present an application to the navigation problem in compressed unranked
trees, represented by forest straight-line programs (FSLPs). We extend a linear
space data structure by Reh and Sieber (2020) by the operation of moving to the
-th child in time where is the degree of the current node.
Contracting SLPs are also applied to the finger search problem over
SLP-compressed strings where one wants to access positions near to a
pre-specified finger position, ideally in time where is the
distance between the accessed position and the finger. We give a linear space
solution where one can access symbols or move the finger in time for any constant where is the -fold
logarithm of . This improves a previous solution by Bille, Christiansen,
Cording, and G{\o}rtz (2018) with access/move time
- …