Combined ILP & RP Graph Transformations #148
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The graph transformation edges break the SeqListScheduler.
The previous UpdateSetupForScheduling(...) function did too much and also clobbered useful information. This changes the code from calling that after each graph transformations pass to having each pass declare what updates it needs, performing only those updates. Removed behavior from removing the call to UpdateSetupForScheduling: - No longer re-allocating all of the info inside each SchedInstruction - No longer re-setting (redundantly) all of the info in each SchedInstruction - No longer recomputing lower and upper bounds. If we have already computed that, we don't want to lose the previously-computed values
This reverts commit 432758d.
Rather than hardcoding the application before or after the heuristic, make it a runtime option. Applying graph transformations before the heuristic has the advantage that the heuristic now has a simpler problem to solve, and thus is more likely to find an optimal solution. Furthermore, the lower bound will be tighter. Applying graph transformations after the heuristic has the advantage that we don't waste time running graph transformations for problems that are already easy; if the heuristic scheduler proves the schedule optimal, we skip graph transformations altogether. Another option is possible: we could do the heuristic first, then if the schedule is not known to be optimal, run graph transformations (as in GT after heuristic), but then re-run the heuristic so that we can potentially skip enumeration. This option is NOT implemented.
The SeqListScheduler is unlikely to find an optimal scheduler, so it is almost certainly better to do graph transformations "before heuristic", meaning---in this case---before the lower bound calculation.
Enables calculating the amount of time these operations took.
Often, it was confusing the direction of the added edge. This fixes it by reading the from/to directly from the added edge.
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The previous conditions could remove an edge (x, y) even if that edge was the reason for the critical path between x and y. These new conditions only consider the path through the newly added edge to avoid that issue.
high_resolution_clock is system_clock in libstdc++.
jrbyrnes
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jrbyrnes
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Aug 25, 2021
jrbyrnes
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Aug 25, 2021
B&B is unlikely to find significant benefit for extremely large regions, once the exponentially larger search space is taken into account. As such, it makes sense to have a knob to disable this scheduling if the region is too large.
The previous name was too generic. This change renames the function to clearly specify what it does.
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Any last thoughts on this PR, or is it ready to submit? |
Looks fine to me |
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Implement RP-preserving ILP graph transformations. Also implement the ability to choose where graph transformations are applied (before or after the heuristic).
This is intended to bring all of my current state of graph transformations into master.