Probabilistic Computing
Abstract
Biological systems
hold the key to ultra-powerful computing using just microwatts of power;
this research explores emulating this behavior in electrical systems. A
novel, biologically inspired computing paradigm is being developed which
could fundamentally change scientific and multimedia computing. This new
computing approach simultaneously addresses a looming problem in
semiconductor systems and many nano-electronics systems; that is, as
feature sizes in computer chips are scaled down further, ideal behavior
cannot always be guaranteed. In these systems, results of individual
operations are described only statistically or probabilistically. A
principal point of this research is to embrace probabilistic computing
elements rather than to devise ways to make them ideal or deterministic.
Recent research suggests that biological and other natural systems are
probabilistic in nature. Thus, probabilistic technology provides a novel
method to simulate biological, chemical, and neurobiological systems to
reach previously unattainable simulation speeds and complexity.
Additionally, many multi-media signal processing systems can take
advantage of this computing approach to achieve tremendous gains in
efficiency at the cost of imperceptible degradation in quality.
Probabilistic CMOS (PCMOS)
allows a computing circuit to operate probabilistically and, as a
result, achieve extreme power savings. A PCMOS circuit is a digital
circuit where the supply voltage is lowered to sub-threshold levels; the
output of the circuit is correct with some probability
p < 1.
The probabilistic nature of the computation may be artificially imposed
or it may be a inevitable result of extreme semiconductor scaling.
Furthermore, p can be precisely controlled using extant analog floating
gate technology. This research uses PCMOS to perform computations and
simulations that either require or can tolerate probabilistic behavior,
specifically simulation of biological processes which can be extended to
Monte Carlo
simulations for any dynamical system. These methods allow
orders-of-magnitude speed-up and substantially reduced power
consumption. The research involves hardware, algorithmic, and
theoretical aspects of probabilistic computing.
Support
- This work is supported by the National Science
Foundation awards #0726969 and #0937177
Publications
- Bo Marr, Jason George, David V. Anderson,
and Paul Hasler, "Increased Energy Efficiency and
Reliability of Ultra-Low Power Arithmetic", International
Midwest Symposium on Circuits and Systems (MWSCAS), p.
366-369, vol. , (2008). Published,
10.1109/MWSCAS.2008.4616812
- Bo Marr, Brian Degnan, David V. Anderson,
and Paul Hasler, "Asynchronously Embedded Datapath for
Performance Acceleration and Energy Efficiency," Proceedings
of the IEEE International Symposium on Circuits and Systems
(ISCAS), p. 3046-3049 , (2009). Published
- Bo Marr, Stephen
Brink, David V. Anderson, Paul Hasler, "A Reconfigurable
Analog System for Efficient Stochastic Biological
Computation", International Symposium on Biomedical Circuits
and Systems, p. 293, vol. , (2008). Published,
10.1109/BIOCAS.2008.4696932
- Jason George, Harry B. Marr, Bilge Akgul, and Krishna
Palem, "Probabilistic Design for Ultra-Low Energy Embedded
Computing", Transactions on Embedded Computing, (2008).
Accepted,
- Richie Wunderlich, Bo Marr, Brian Degnan, Paul Hasler,
"A Low Power Floating-Gate FPGA", Custom Integrated Circuits
Conference (CICC), p. , vol. , (2009). Submitted,
- Bo Marr, Arindam Basu, Stephen Brink, Paul Hasler, "A
Learning Digital Computer", Design Automation Conference
(DAC), (2009). Accepted,
- Bo Marr, Jason George, Brian Degnan, Paul Hasler, David
V. Anderson, "Error Immune Logic for Low Power Probabilistic
Computing", Journal of VLSI Design, (2009). Submitted,
- Bo Marr, Stephen
Brink, Paul Hasler, David V. Anderson, "A Reconfigurable,
Probabilistic Hardware for Fast Dynamical Systems," IEEE
Transactions on Circuits and Systems I, (2009). Submitted,
Findings and Resources
Probabilistic Computing Resources
- The VISEN Center at
Rice University is directed by co-PI Krishna Palem
Recent Findings
-
A General Theory of Probabilistic Dynamical Systems: any dynamical system can be represented by a PCMOS system, both those that are
random and deterministic by nature including biological, chemical, and nuclear systems [as
reported in submitted TCAS I paper]. This theory was proven by
implementing this on a reconfigurable chip, the Reconfigurable Analog Signal Processor (RASP) where probabilistic computation was
successful.
-
Neuromorphic and bio-inspired structures have been developed where the hardware itself 'learns' using floating gate technology [Marr et al,
DAC, 2009]. The hardware learns and improves errors, power, and speed based on results from inputs. A chip has been produced with this
technology.
-
A plot of real data from a probabilistic circuit on the reconfigurable RASP chip can be seen in [Marr et al, TCAS I, 2009] shows that we can
control p, the probability of correctness for a single gate, to within about +/-2% error.
-
A prototype chip 'Reaction Gates' has been built. With the RASP reconfigurable chip, individual units do a single operation that simulates a
reaction have been built that have resulted in 130X performance improvement over biological system simulations [Marr et al., BioCAS,
2008],[Marr et al., TCAS I, 2009 (submitted)].