Stoica: Adaptive and Evolvable Hardware 1 JPL Co-PIs:Didier Keymeulen and Ricardo Zebulum Adrian Stoica NASA Jet Propulsion Laboratory California Institute of Technology Adaptive and Evolvable Hardware 11/28/2006 DSRC Workshop on Adaptive Electronics

Stoica: Adaptive and Evolvable Hardware 2 Outline  Vision, motivation  Adaptive hardware characteristics  Limitations  Evolvable hardware  Open problems  Possible paths

Stoica: Adaptive and Evolvable Hardware 3 Vision for adaptive, intelligent devices Deploy 1 a miniature 2 device in an unknown environment 3. Provide a high-level specification of intended function 4. The device adapts itself to provide the function intelligently 5. 1 (drop, plug-in, etc); 2 (finger-nail size?); 3 (enemy field, remote planet, unknown computer); 4 (operation, mission); 5 (/optimally select/determine algorithms, protocols, resources to use, etc). Adaptation Environments Mismatches in fabrication Faults New functionsNew users Provide the function that is needed, when is needed  Vision, motivation

Stoica: Adaptive and Evolvable Hardware 4 Real-world needs for adaptive HW Adaptive computing - problem/algorithm dependent efficient resource utilization (efficient algorithmic mapping, maximal speed, minimal power) Adaptive signal processing - optimization/improvements of adaptive compression, compressive sampling, Adaptive communications - optimizing bandwidth, avoiding jamming/EW, etc, Fault-tolerant computing - dealing with low reliability, imprecise/imperfect components, natural/terrorist induced catastrophes (EMG pulse, radiation) taking over functions from other resources that were damaged  Vision, motivation

Stoica: Adaptive and Evolvable Hardware 5 Automatic in-situ synthesis of a totally new hardware configuration is needed: Dramatic changes in hardware/environment (e.g. from radiation and extreme temperatures), or Need for new functions (e.g. in case of opportunistic science or mission changes) NASA Motivation: Surviving longer missions (100+ years) and harsher environments Survive, Adapt, Evolve Environments Faults/degradation New roles Aging Causes of internal/external changes:  Vision, motivation

Stoica: Adaptive and Evolvable Hardware 6 What kind of adaptation we want Continuous, no system down time/interrupts for adaptation Timely, as fast as needed, rapid reaction Harmonious, correlated at different levels of system hierarchy User- Friendly in setting new adaptation objectives Lean, with minimal overhead for adaptation  Vision, motivation

Stoica: Adaptive and Evolvable Hardware 7 Adaptive and evolvable hardware In a restricted sense it means modifying its behavior under the control of an evolutionary algorithm word ‘evolution’ indicates progress  Adaptive hardware characteristics Adaptive hardware: hardware able to change itself (self-reconfigure) in order to optimize its behavior in response to an internal objective and external environment Evolvable hardware – a special case of adaptive hardware mainly driven by internal objectives; performance consistently improves in time word ‘evolution’ indicates technique

Stoica: Adaptive and Evolvable Hardware 8 Characteristics of Adaptive Hardware 1.Hardware can change – reconfigurable HW (RH) 2. Has a decision-maker/controller that changes the hardware – reconfiguration algorithm (RA) 3. An objective function that guides the change; this could be built-in, passed-on by other hardware components, or by user  Adaptive hardware characteristics

Stoica: Adaptive and Evolvable Hardware 9 AutoRe-custom. Making hardware that can change: Industry has provided for increased post- manufacturing customization Dynamic Re-custom. Triggered Re-custom. In-Situ Re-custom. Field Custom.Lab. Custom. Post-Manufacturing CustomizationPre-Manufacturing Customization Manufacturing Re-custom. Adapted after Plura-Tech presentation by Radu Andrei, AHS 2006 In response to user needs Rapid development Upgrades to cope with standards/fixes As a solution to mitigate technology limitations Manufacturing imperfections at lower feature size  Adaptive hardware characteristics

Stoica: Adaptive and Evolvable Hardware 10 Limitations of current reconfigurable devices No HW Decision-maker: Only SW implementations for for system-level adaptation Where hardware changes under SW control: –Simple objective functions –Time/resource consuming to reprogram the chip research in dynamic reconfiguration, partial reconfiguration, context switching Extreme overheads on current reconfigurable devices!  Limitations

Stoica: Adaptive and Evolvable Hardware 11 Hardware changes – research devices Reconfigurable –configurations can be changed, by mapping a different topology (digital control) –switch based architecture (not always, e.g. reconfigurable robots) –functional change (not always, e.g. self-repair) –often by resource reuse Morphable – functional change without switches, by analog control, more gradual/continuous Adjustable/Tunable/Parametric –changes the parameters of a function Changes in reconfigurable architectures -function in Configurable Blocks (CB) –Digital or Analog Building block Logic function Transistor, OpAmp, dedicated circuits (filters, analog multipliers) Heterogeneous Arrays -interconnect between CBs: -On/off switches; also switched capacitors. Programmable: that can be programmed/changed, e.g. Field Programmable Arrays  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 12 Hardware that changes – Examples of JPL Reconfigurable Analog Arrays Field Programmable Analog Array Self-Reconfigurable Analog Array AnadigmJPL Field programmable, switches Field-programmable, switches, built-in algorithms Under external control Under internal control (self) -40C to 85C-180 to 125C No rad-toleranceRad-hard FTPA-0 cell FTPA-2 cell FTPA cellular architecture  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 13 Implementing reconfiguration algorithms Model-based: Memory-based: predetermined contexts stored in memory configurations that correspond to various contexts; Calculate an (analytic) solution Search-based, HW in the loop: Gradient-based search/optimization guides reconfiguration to increasingly better performance; Population-based search (e.g. using evolutionary algorithms)- if there is no predetermination and no simple change algorithm Limitations: –it is computationally intensive –may go through states which are actually worse that where it was started and can potentially harm the system if control is maintained from the reconfigurable analog area.  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 14 Evolutionary Algorithm Search on a population of chromosomes select the best designs from a population reproduce with variation iterate till goal is reached Evaluate responses, assess fitness Target response or quality metrics Chromosomes Control bitstrings Conversion to a circuit description Circuit response Reconfigurable hardware Monitor response. If not good, change/tune. Repeat Evolution-based reconfiguration  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 15 Example of evolvable hardware in parametric correction (calibration/compensation) of OTA-based circuit functionality: OUT Algorithm determines correction needed Configuration Bits G m 1 i B1 G m 4 G m 2 G m 3 IN Register Download i B4 i B2 i B3 Calibration Higuchi, (Japan) used this compensation circuit to improve yield JPL used to a similar scheme to compensate for temperature ( Gm : Transconductance Amplifier )  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 16 Self-Reconfigurable Analog Arrays SRAA are reconfigurable analog arrays that are configured by reconfiguration algorithms (mapped in digital circuits), which –detect circuit performance degradations due to faults/drifts caused by temperature and radiation –compensate for those by changing to another, more appropriate configuration, pre-determined or computed in-situ. Digital part (more robust) provides correction controls for analog (more sensitive) Reconfiguration Algorithm (digital) Reconfigurable Analog Array Self-reconfigurable analog array  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 17 Reconfigurable Analog Array (RAA) programming Correct drifts/deviations: Evaluate deviation from specifications Determine algorithmic correction Apply it by changing: configuration (change of circuit topology) programmable compensation (e.g. programmable current bias) Configuration change In array of cells Parameter change G cab V1V1 V2V2 V out cell  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 18 Iout (A) 22C OTA drift at low temperature is recovered by change in bias voltage Vdd:3.1V, V1:1.5V, V2:0-3.0V, V(Iout):2V Vb: 1.0V Vb: 0.9V Vb: V -180C 22C, Vb: 0.8V Vb: 0.95V Vb: 0.85V -180C, Vb: 0.8V Iout (A) 22C 0C -30C -60C -90C -120C -150C -180C Vbias:0.8V OTA Sweep 25C/0.8V -180C/0.85V  Increase Vbias from 0.8 to 0.85V recovers curve at Room temperature  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 19 Demonstrated Temperature Compensation by Reconfiguration/Tuning Entire system digital and analog demonstrated to survive from -180C to 120C at 22C degraded -180C recovered -180C Input Output Degraded output Partial recovery Thermal testing station Degraded output and recovery  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 20 Movie 2

Stoica: Adaptive and Evolvable Hardware 21 System-level block diagrams SRAA Analog ASIC Test Fixture RAC Array FAC Array SwitchBox (SB) Array and Configuration Logic Digital ASIC Genetic Algorithm Engine (GA) Memory Module Main Controller Module User GA parameters System Monitoring Module Fitness Evaluation Module 2 (FEM2) Digital Control2 (DC2) Digital Control1 (DC1) FPGA Fitness Evaluation Module 1 (FEM1) GA/GD Model-based Compensation Module Current Temperature Honeywell SOI-5 SRAA-2 and Digital ASIC In1 2 In2 Out In1 1 In2 Out In1 4 In2 Out In1 3 In2 Out Quad OpAmp In1 6 In2 Out In1 5 In2 Out In1 8 In2 Out In1 7 In2 Out HV OpAmp In1 10 In2 Out In1 9 In2 Out In1 12 In2 Out In1 11 In2 Out Ping-pong OpAmp In1 14 In2 Out In1 13 In2 Out In1 16 In2 Out In1 15 In2 Out High Speed Comparator 17 I out Current Source 18 I out 19 I out 20 I out In1 22 In2 Out In1 21 In2 Out In1 24 In2 Out In1 23 In2 Out Comp2  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 22 Lessons Learned - RH Characteristics needed by evolvable devices: –Can be reconfigured many times –All configurations are safe for the device (No configuration that harms the device can be programmed) –Repeatability: Similar behavior every time for same configuration Commercial devices have been used only moderately but there is an increasing trend for their use. –Advantages: Available and affordable Complex enough to do real world applications easily –Disadvantages: Better ones (easier to program, direct access to lowest levels, possibly protected by company secrets, development kits, SDKs) would be useful Somehow complex to program to do a full application  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 23 Lessons Learned - RA All (almost all) evolutionary techniques work on simple problems, efficiency depends on the problem None was demonstrated on really difficult problems EAs require to many iterations for really complex problems (the main time is usually spent in evaluating the RH in each iteration) so are slow Not only they are slow but may go through undesirable states if RH is used in direct loop to control a real system Use of domain knowledge helps But many real world problems – require application specific designs, but the search problems themselves may not always be hard  Evolvable Hardware

Stoica: Adaptive and Evolvable Hardware 24 Challenges related to reconfiguration mechanisms and evolution 1.Scalability – without hierarchy – divide and conquer works but can we determine fitness for subproblems automatically – automatic hierarchical partitioning without a library of building blocks of various granularity 2.On-line evolution: Going through undesirable states – ping pong architectures 3.Reduce system overhead, e.g. for fitness evaluation/ reconfiguration 4.Integration in accepted design (…) flows. 5.Means to specify an evolvable system component at system level, behavioral models  Open Problems –Solution is guarantied only where tested

Stoica: Adaptive and Evolvable Hardware 25 Challenges related to reconfigurable hardware Current overhead and cost for building more flexible devices goes up DoD needs a solution that is economically attractive for the industry – overhead must go down One needs to tale customization of a system to a lower level –System block level customization –Hardware block level customization –Transistor level customization –……… Task Funct. 1 Funct. 2 Funct. n Funct. 1.1 Funct. 1.2 Funct. 1.n Funct Funct Funct. 1.1.n System Block (SW/HW) Hardware Block (HW/FW) Manufacturing Layers Transistor (HW)  Open Problems

Stoica: Adaptive and Evolvable Hardware 26 Objective: higher efficiency of adaptability FPGA-level Adaptability Number of building blocks Inefficiency level (logarithmic scale) building block inefficiency ( %) customization inefficiency Transistor-level Adaptability Number of building blocks building block inefficiency (~10%) Inefficiency level (logarithmic scale) customization inefficiency (~10%) FPGA-level adaptability –Building blocks use a number of basic elements (transistors) Creates a % overhead –Heterogeneous structure (building blocks have pre-determined functions) Topological inflexible structure (building block position determined before manufacturing) Utilization rate decreases exponentially with the number of building blocks Can be marginally improved through topological rearrangement of building blocks Transistor-level adaptability –Building blocks use one single basic element (transistor) Overhead should be not bigger than 10% –Homogeneous structure (building block functionality is programmable after manufacturing) Utilization rate can theoretically stay at full level, regardless of number of building blocks  Possible paths

Stoica: Adaptive and Evolvable Hardware 27 Reducing flexibility/adaptability overheads - classical DARPA-hard problems Flexibility/configuration overhead –From current over 5-10x penalty (area) To 0.1x for flexible devices (100 times) + ~ 0.1x for self-configuration/adaptation Transistor-level or below Self-reconfiguration overhead –From current computing of reconfiguration solution in minutes To ms and below (1000x) Distributed architecture No A/D and D/A for monitoring signal changes  Possible paths

Stoica: Adaptive and Evolvable Hardware 28 Diffusing intelligence to fine HW levels in Intelligent Integrated Microsystems (I 2 M) Embedded intelligence is needed to use flexibility – and achieve adaptation/evolution It empowers the HW, making use of HW flexibility (e.g. configurability, at various levels of reconfigurable hardware) to obtain more performance than what is possible with software-only solutions. Fine HW levels, flexible, configurable Algorithms/built-in mechanisms for optimization (adaptation/evolution) Within/between Types of HW: electronics, MEMS/BioMEMS, Optical, Antennas Modules in info processing chain: sensing, pre-processing, ADC, compression, etc. Levels of granularity: function block, gate, transistor, below transistor  Final remarks

Stoica: Adaptive and Evolvable Hardware 29 Additional slides

Stoica: Adaptive and Evolvable Hardware 30 Evolution on SABLES Evolution of a Half-wave rectifier circuit: Excitation input of 2kHz sine wave of amplitude 2V –9% elite percentage, 70% crossover, 4% mutation; 100 individuals population; –20 seconds experiments Stimulus-Response wave form during the evaluation of a population in one generation (left) and for 3 individuals in the population (right)

Stoica: Adaptive and Evolvable Hardware 31 Half-wave rectifier convergence Results of the evolution of a halfwave rectifier during and after evolution are shown 100 individuals are evaluated (elite 9% set aside, 70% rate for crossover, 4% for mutation) on two cells AB CD Best individuals of generations #1, 5, 50 & 82 (A - D respectively) Input (2kHz) and solution at generation 82

Stoica: Adaptive and Evolvable Hardware 32 Frequency Specifications for the IF filter: tuning Frequency (kHz) Gain (dB) Gain (dB) Frequency (kHz) Spec. ( -3dB Points) Ideal Response From presentation by T. Higuchi, Japan, at EH-2003

Stoica: Adaptive and Evolvable Hardware 33 Self-Reconfigurable Electronics in Extreme Environments Digital System – A High Level View RAC = Reference Analog Cell FAC = Functional Analog Cell Two Compensation Modes Model Look-Up Table based compensation Implementation of a pre-characterized correction voltages for each RAC Genetic Algorithm based compensation Implements an evolutionary approach to find the best set of Vbias values (initial population is random) Find best set of bias voltages (Vbest) Select Next RAC Excite & Evaluate Satisfactory? Yes No Apply Vbest to FACs Initialize Monitor Compensate Digital ASIC Reconfigurable Analog Array (RAA) Digital ASIC Functionality Continuous Monitoring of Analog Function

Stoica: Adaptive and Evolvable Hardware 34 System-level integration- board-level SRAA RAA IC FPGA V II Pro PC For experiment set-up and data monitoring display ADC LTC1745 DAC AD9772 DAC AD9772 RAA Digital Control Scope Extreme Environment Xilinx proto-board running reconfiguration algorithms VBias0 VBias1 Vin0 Vout 5V 3.3V Filtered signal R[3:0]C[2:0]Nandc Data RAA board DAC AD V 1.5V Vref0 14 CLK 43 CLK_OUT ENC 12 RS232

Stoica: Adaptive and Evolvable Hardware 35 SRAA board level integration DAC Monitoring and Compensation DAC ADC Power RAA FPGA Vbias Control for RAA Analog Filtering Signal Extraction RAA Topology Control (from FPGA) Excitation Signal for RAA Serial Inter- face

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