slide 10 of 21
Barrier Synchronization
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An arbitrary group of PCs can participate
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No PC executes past a barrier until all have arrived
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Two-cycle barriers using two barrier units:
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Output: present at barrier, reset barrier'
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Input: poll for all PCs present
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Synchronization time:
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< 0.1 us logic, < 0.2 us cable, 1 us port register
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Total < 3 us for 4 PCs; < 7 us for 2,000+ PCs