Apparatus and methods for synaptic update in a pulse-coded network

• US 9,147,156 B2
• Filed: 09/21/2011
• Issued: 09/29/2015
• Est. Priority Date: 09/21/2011
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Levin, Jeffrey Alexander, Izhikevich, Eugene M., Rangan, Venkat, Piekniewski, Filip, MALONE, Erik Christopher, Nageswaran, Jayram Moorkanikara
• Primary Examiner(s): Gaffin, Jeffrey A
• Assistant Examiner(s): Afolabi, Ola Olude
• Application Number:
  US13/239,255
• Publication Number:
  US 20130073491A1
• Time in Patent Office: 1,469 Days
• Field of Search: 706/23, 706/27
• US Class Current: 1/1
• CPC Class Codes: G06N 3/049 Temporal neural networks, e.g. delay elements, oscillating neurons or pulsed inputs

Abstract

Apparatus and methods for efficient synaptic update in a network such as a spiking neural network. In one embodiment, the post-synaptic updates, in response to generation of a post-synaptic pulse by a post-synaptic unit, are delayed until a subsequent pre-synaptic pulse is received by the unit. Pre-synaptic updates are performed first following by the post-synaptic update, thus ensuring synaptic connection status is up-to-date. The delay update mechanism is used in conjunction with system “flush” events in order to ensure accurate network operation, and prevent loss of information under a variety of pre-synaptic and post-synaptic unit firing rates. A large network partition mechanism is used in one variant with network processing apparatus in order to enable processing of network signals in a limited functionality embedded hardware environment.

Claims

1. A method for updating a communication channel, in a computerized spiking network apparatus, based at least in part on a first triggering pulse and a second triggering pulse communicated through the communication channel, the method comprising:

providing a first update based at least in part on a first interval between the first triggering pulse and an earliest subsequent pulse associated with a post-synaptic unit;

providing a second update based at least in part on a second interval between the second triggering pulse and a latest pulse associated with the post-synaptic unit; and

storing information related to a plurality of output pulses generated by the post-synaptic unit, the plurality of output pulses comprising the earliest subsequent pulse;

wherein the communication channel is configured to connect a pre-synaptic unit to the post-synaptic unit.

2. The method of claim 1, wherein:

the first update and the second update are evaluated in response to the second triggering pulse; and

the first update precedes the second update.

3. The method of claim 2, further comprising:

storing information related to at least one output pulse of the plurality of output pulses being generated at a first time by the post-synaptic unit, prior to the second triggering pulse; and

storing information related to a second input pulse received at a second time at the post-synaptic unit, prior to the first time.

4. The method of claim 3, wherein:

the first update is configured based on a first plurality of intervals between the first triggering pulse and individual ones of the plurality of output pulses; and

the second update is configured based on a second plurality of intervals between the second triggering pulse and the plurality of output pulses.

5. The method of claim 1, further comprising:

storing information related to at least one output pulse of the plurality of output pulses being generated at a first time by the post-synaptic unit, prior to the second triggering pulse; and

storing information related to a second input pulse received at a second time at the post-synaptic unit, prior to the first time.

6. The method of claim 1, further comprising:

modifying a state associated with the post-synaptic unit based at least in part on the updating;

wherein the second update is performed subsequent to the performing the first update yet prior to the modifying the state.

7. The method of claim 1 wherein:

the information related to the plurality of output pulses is stored in a first memory device;

storing information related to the communications channel in a second memory device; and

the second memory device is configured by a first access time that is greater than a second access time of the first memory device.

8. The method of claim 1, wherein:

the first update comprises a first plurality of updates configured based on a first plurality of intervals between the first triggering pulse and individual ones of the plurality of output pulses; and

the second update comprises a second plurality of updates configured based on a second plurality of intervals between the second triggering pulse and the plurality of output pulses.

9. The method of claim 8, wherein:

the updating the communication channel comprises modifying a parameter associated with the communication channel;

where individual ones of the first plurality of updates and second plurality of updates comprise modifications of the parameter; and

the method further comprises storing the parameter in a second memory device via a single transaction with the second memory device.

10. The method of claim 9, wherein the parameter comprises a channel weight;

and

the single transaction is configured to reduce a bus overhead of the second memory device.

11. A computer implemented method of operating a communications channel in a computerized spiking neuronal network, the method comprising:

modifying the communications channel based at least in part on an interval between a current trigger and a latest preceding pulse associated with a post-synaptic unit coupled to the communications channel;

maintaining the communications channel substantially unmodified between the current trigger and an immediately preceding trigger;

adjusting, subsequent to modifying the communications channel, a state of the post-synaptic unit based at least in part on the current trigger, the communications channel configured to connect a pre-synaptic unit to the post-synaptic unit; and

subsequent to the modifying the communications channel, adjusting a state of the post-synaptic unit based at least in part on the current trigger;

wherein, individual ones of the immediately preceding trigger and the current trigger are configured to be communicated through the communications channel.

12. The method of claim 11, wherein:

the modifying the communications channel comprises determining an updated channel weight; and

adjusting the state using the updated channel weight.

13. The method of claim 11, wherein the method further comprises:

prior to adjusting the state, adapting the communications channel based on a second interval between the immediately preceding trigger and an earliest subsequent pulse associated with the post-synaptic unit.

14. The method of claim 13, wherein:

the adapting and the modifying the channel cooperate to determine an updated channel weight;

and the method further comprises adjusting the state based at least in part on the updated channel weight, the adapting the communications channel being delayed until the adjusting of the state.

15. The method of claim 14, further comprising:

storing in a first memory device the interval between the immediately preceding trigger and the earliest subsequent pulse; and

storing the updated channel weight in a second memory device via a single memory transaction;

wherein the second memory device is configured by a first access time that is greater than a second access time of the first memory device.

16. The method of claim 15, wherein:

the communications channel is configured by a conduction delay; and

the updated channel weight is stored in the second memory device based at least in part on the conduction delay.

17. A computer implemented method of operating a communications channel in a computerized spiking neuronal network, the method comprising;

transmitting trigger pulses from a pre-synaptic unit through the communications channel to a post-synaptic unit;

performing a first update based at least in part on a first interval between a trigger pulse of at least one trigger pulse and an earliest subsequent pulse associated with the post-synaptic unit coupled to the communications channel;

subsequent to performing the first update, performing a second update based at least in part on a second interval between the trigger pulse and a latest preceding pulse associated with the post-synaptic unit; and

adjusting a state of the post-synaptic unit based at least in part on a current trigger, the second interval based at least in part on the current trigger;

wherein individual ones of the first update and the second update are evaluated in response to the trigger pulse.

18. The method of claim 17, wherein individual ones of the first update and the second update are evaluated prior to the adjusting the state.

19. The method of claim 18, further comprising storing the first interval in a storage apparatus, the storing being effectuated prior to another trigger pulse, the another trigger pulse occurring subsequent to the trigger pulse.

20. The method of claim 19, wherein:

the first update and the second update cooperate to determine an updated channel parameter; and

the updated channel parameter is stored in a memory device via a single memory bus transaction, the single memory bus transaction configured to reduce memory access overhead.

21. The method of claim 17, wherein the first update and the second update are evaluated at a time associated with the current trigger.

22. The method of claim 17, wherein:

the first interval is based on a first trigger and the earliest subsequent pulse associated with the post-synaptic unit;

the second interval is based on a second trigger and the latest preceding pulse associated with the post-synaptic unit; and

the first trigger comprises a trigger immediately preceding the second trigger.

23. The method of claim 22, further comprising storing the first interval in a storage apparatus, the storing being effectuated prior to a third trigger, the third trigger occurring subsequent to the first trigger.

24. The method of claim 23, wherein:

the first update and the second update cooperate to determine an updated channel parameter; and

the updated channel parameter is stored in a memory device via a single memory bus transaction, the single memory bus transaction configured to reduce memory access overhead.

25. The method of claim 17, wherein the earliest subsequent pulse associated with the post-synaptic unit comprises the latest preceding pulse associated with the post-synaptic unit.

26. A computerized spiking network apparatus comprising at least one node coupled to a communications channel in the computerized spiking network apparatus, the computerized spiking network apparatus comprising a processor and further comprising:

means for updating the communications channel based at least in part on an interval between a current trigger and a latest preceding pulse associated with the at least one node;

means for maintaining the communications channel substantially unmodified between the current trigger and an immediately preceding trigger; and

means for communicating the current trigger and the latest preceding pulse through the communications channel;

wherein;

the means for updating comprises means for effecting an update with a single transaction of a memory bus, the single transaction reducing memory bus overhead; and

the means for updating the communications channel is based at least in part on a plurality of pulses associated with the at least one node.

27. The apparatus of claim 26, further comprising:

means for updating one other channel the communications channel based on one other interval between the current trigger and one other latest preceding pulse associated with one other node;

wherein;

individual ones of the communications channel and the one other channel are configured to communicate the current trigger; and

the means for updating the communications channel and means for updating the one other channel are effected by the single transaction of the memory bus.

28. A method of updating a first and second channels in a computerized spiking neuronal network, the method comprising:

performing a first update based at least in part on a first interval between a first trigger and a first earliest subsequent pulse associated with a first post-synaptic unit coupled to a first channel, where a pre-synaptic unit is coupled via the first channel to the first post-synaptic unit;

performing a second update based at least in part on a second interval between a second trigger and a first latest preceding pulse associated with the first post-synaptic unit;

performing a third update based at least in part on a third interval between the first trigger and a second earliest subsequent pulse associated with a second post-synaptic unit coupled to a second channel, where the pre-synaptic unit is coupled via the second channel to the second post-synaptic unit; and

performing a fourth update based at least in part on a fourth interval between the second trigger and a second latest preceding pulse associated with the second post-synaptic unit.

29. The method of claim 28, wherein, the first and the second trigger are communicated through individual ones of the first and the second channels.

30. The method of claim 29, further comprising:

storing in a first storage apparatus information related to a plurality of output pulses generated by at least one of the first post-synaptic unit and the second post-synaptic unit, the plurality of output pulses comprising at least one of the first earliest subsequent pulse and the second earliest subsequent pulse.

31. The method of claim 30, wherein:

the first update and the second update cooperate to determine a first updated parameter associated with the first channel;

the third update and the fourth update cooperate to determine a second updated parameter associated with the second channel; and

the method further comprises storing, in a second storage apparatus, the first updated parameter and the second updated parameter via a single bus transaction of the second storage apparatus.

32. The method of claim 31, wherein:

the first updated parameter comprises a first channel weight and the second updated parameter comprises a second channel weight; and

the single bus transaction is configured to reduce bus access overhead of the second storage apparatus.

33. The method of claim 31, wherein the second storage apparatus is configured by a first access time that is greater than a second access time of the first storage apparatus.

34. The method of claim 31, wherein:

the first channel and the second channel are configured by conduction delays; and

the first updated parameter and the second updated parameter are stored in the second storage apparatus based at least in part on the conduction delays.