SUPS

Computing

For a processor or computer designed to simulate a neural network SUPS is measured as the product of simulated neurons N and average connectivity c (synapses) per neuron per second:

S U P S = c × N

Depending on the type of simulation it is usual equal to the total number of synapses simulated.

In an "asynchronous" dynamic simulation if a neuron spikes at υ Hz, the average rate of synaptic updates provoked by the activity of that neuron is υ c N . In a synchronous simulation with step Δ t the number of synaptic updates per second would be c N Δ t . As Δ t has to be chosen much smaller than the average interval between two successive afferent spikes, which implies Δ t < 1 υ N , giving an average of synaptic updates equal to υ c N 2 . Therefore, spike-driven synaptic dynamics leads to a linear scaling of computational complexity O(N) per neuron, compared with the O(N²) in the "synchronous" case.

Records

Developed in the 1980s Adaptive Solutions' CNAPS-1064 Digital Parallel Processor chip is a full neural network (NNW). It was designed as a coprocessor to a host and has 64 sub-processors arranged in a 1D array and operating in a SIMD mode. Each sub-processor can emulate one or more neurons and multiple chips can be grouped together. At 25 MHz it is capable of 1.28 GMAC.

After the presentation of the RN-100 (12 MHz) single neuron chip at Seattle 1991 Ricoh developed the multi-neuron chip RN-200. It had 16 neurons and 16 synapses per neuron. The chip has on-chip learning ability using a proprietary backdrop algorithm. It comes in a 257-pin PGA encapsulation and develops 3.0 W (max). It was capable of 3 GCPS (1 GCPS at 32 MHz).

In 1991-97, Siemens developed the MA-16 chip, SYNAPSE-1 and SYNAPSE-3 Neurocomputer. The MA-16 is a fast matrix-matrix multiplier that can be combined to form systolic arrays. It can process 4 patterns of 16 elements each (16-bit), with 16 neuron values (16-bit) at a rate of 800 MMAC or 400 MCPS at 50 MHz. The SYNAPSE3-PC PCI card contains 2 MA-16 with a peak performance of 2560 MOPS (1.28 GMAC); 7160 MOPS (3.58 GMAC) when using three boards.

In 2013, the K computer was used to simulate a neural network of 1.73 billion neurons with a total of 10.4 trillion synapses (1% of the human brain). The simulation ran for 40 minutes to simulate 1 s of brain activity at a normal activity level (4.4 on average). The simulation required 1 Petabyte of storage.