Contention detection and resolution
First Claim
1. A method of resolving contention in addressed memory updating in which a memory location having a specific location identifier can be updated substantially simultaneously from a plurality of sources, said method comprising the steps of:
- (i) utilizing an updating format for the signal or packet carrying out the updating, said format comprising the specific identifier of the memory location to be updated, the content with which said memory location is to be updated, and a resident updating count of the updating source, said count comprising a number indicative of the position of the updating message in the sequence of occasions on which the updating source has been updated inclusive of the current updating;
(ii) storing for each receiving memory location the updating count of the previously received updating;
(iii) comparing the updating count presently resident at the receiving memory location with the updating count of any currently received updating signal or packet, and(iv) if the currently received updating count is greater than the presently resident updating count, not actioning the incoming signal or packet;
or(v) if the currently received updating count is less than the currently resident updating count, actioning the incoming signal or packet;
or(vi), if the currently received updating count is equal to the presently resident updating count, instituting a contention resolution.
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Accused Products
Abstract
A multiple computer system is disclosed in which n computers (M1, M2 . . . Mn) each run a different portion of a single application program written to execute only on a single computer. The local memory of each computer is maintained substantially the same by updating all computers with every change made to addressed memory locations. Contention can arise when the same memory location is substantially simultaneously updated by two or more machines because of transmission delays and latency of the communications network interconnecting all the computers. In particular a method of detecting and resolving contention is disclosed which utilizes a count value indicative of the number of the sequence of occasions on which each memory location has been updated. Contention is indicated if the currently stored count value and the incoming updating count value are the same. The contention can be resolved by providing a further rule. One such further rule is that in the presence of contention the updating message from the higher numbered computer is to be accepted and the updating message from the lower numbered computer is to be rejected. Other further rules are also disclosed.
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Citations
17 Claims
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1. A method of resolving contention in addressed memory updating in which a memory location having a specific location identifier can be updated substantially simultaneously from a plurality of sources, said method comprising the steps of:
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(i) utilizing an updating format for the signal or packet carrying out the updating, said format comprising the specific identifier of the memory location to be updated, the content with which said memory location is to be updated, and a resident updating count of the updating source, said count comprising a number indicative of the position of the updating message in the sequence of occasions on which the updating source has been updated inclusive of the current updating; (ii) storing for each receiving memory location the updating count of the previously received updating; (iii) comparing the updating count presently resident at the receiving memory location with the updating count of any currently received updating signal or packet, and (iv) if the currently received updating count is greater than the presently resident updating count, not actioning the incoming signal or packet;
or(v) if the currently received updating count is less than the currently resident updating count, actioning the incoming signal or packet;
or(vi), if the currently received updating count is equal to the presently resident updating count, instituting a contention resolution. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for detecting contention in addressed memory updating, said system comprising:
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at least one memory location having a specific location identifier; a plurality of sources each of which can update said memory location(s) and each of which utilizes an updating format for the signal or packet carrying out the updating, said format comprising the specific identifier of the memory location to be updated, the content with which said memory location is to be updated, and a resident updating count of the updating source, said count comprising a number indicative of the position of the updating message in the sequence of occasions on which the updating source has been updated inclusive of the current updating; a storage means associated with each said memory location and in which the updating count of the previously received updating is stored; comparison means to compare the previously stored updating count with the updating count of any currently received updating signal or packet; contention indicating means connected with said comparison means and operable to indicate a contention situation if the compared updating counts are the same, to not act upon the currently received updating signal or packet if said comparison indicates that the currently received updating count is greater than the presently resident updating count, or to act upon the currently received updating signal or packet if said comparison indicates that the currently received updating count is less than the presently resident updating count, and contention resolution means connected with said contention indicating means to institute a contention resolution procedure. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification