[TKET-1598] fix ConnectivityPredicate fails after FullPeepholeOptimise and AASRouting #194
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alexcowtan
requested changes
Feb 2, 2022
Comment on lines
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762
| while (circ.has_implicit_wireswaps()) { | ||
| bool foundswap = false; | ||
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| qubit_map_t perm = circ.implicit_qubit_permutation(); | ||
| for (const std::pair<const Qubit, Qubit> &pair : perm) { | ||
| if (pair.first != pair.second) { | ||
| if (!foundswap) { | ||
| circ.replace_implicit_wire_swap(pair.first, pair.second); | ||
| foundswap = true; | ||
| } | ||
| } | ||
| } | ||
| } |
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Is the foundswap variable really necessary? Can you not do something like:
Suggested change
| while (circ.has_implicit_wireswaps()) { | |
| bool foundswap = false; | |
| qubit_map_t perm = circ.implicit_qubit_permutation(); | |
| for (const std::pair<const Qubit, Qubit> &pair : perm) { | |
| if (pair.first != pair.second) { | |
| if (!foundswap) { | |
| circ.replace_implicit_wire_swap(pair.first, pair.second); | |
| foundswap = true; | |
| } | |
| } | |
| } | |
| } | |
| while (circ.has_implicit_wireswaps()) { | |
| qubit_map_t perm = circ.implicit_qubit_permutation(); | |
| for (const std::pair<const Qubit, Qubit> &pair : perm) { | |
| if (pair.first != pair.second) { | |
| circ.replace_implicit_wire_swap(pair.first, pair.second); | |
| } | |
| } | |
| } | |
| } |
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Without the variable only one swap will create an infinity loop. The replace_implicit_wire_swap will remove one implicit wire swap and then add it again in the next iteration of the loop where pair.first != pair.second.
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Ah, okay. Would it be slightly faster then to have a break rather than keep iterating through the loop but not replacing the swaps?
Co-authored-by: Alexander Cowtan <[email protected]>
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This is fixing #97
The problem has been a wrong handling of the implicit wire swaps in the aas pass