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router2: Add a simple timing heuristic

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Signed-off-by: David Shah <dave@ds0.me>
This commit is contained in:
David Shah 2020-02-03 13:33:20 +00:00
parent ce144addb3
commit a8206ed170
1 changed files with 27 additions and 0 deletions
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27
common/router2.cc
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@ -36,6 +36,7 @@
#include <thread>
#include "log.h"
#include "nextpnr.h"
#include "timing.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
@ -61,6 +62,7 @@ struct Router2
// Coordinates of the center of the net, used for the weight-to-average
int cx, cy, hpwl;
int total_route_us = 0;
float max_crit = 0;
};
struct WireScore
@ -111,6 +113,10 @@ struct Router2
// Use 'udata' for fast net lookups and indexing
std::vector<NetInfo *> nets_by_udata;
std::vector<PerNetData> nets;
// Criticality data from timing analysis
NetCriticalityMap net_crit;
void setup_nets()
{
// Populate per-net and per-arc structures at start of routing
@ -1024,8 +1030,29 @@ struct Router2
for (size_t i = 0; i < nets_by_udata.size(); i++)
route_queue.push_back(i);
bool timing_driven = ctx->setting<bool>("timing_driven");
do {
ctx->sorted_shuffle(route_queue);
if (timing_driven && (int(route_queue.size()) > (int(nets_by_udata.size()) / 50))) {
// Heuristic: reduce runtime by skipping STA in the case of a "long tail" of a few
// congested nodes
get_criticalities(ctx, &net_crit);
for (auto n : route_queue) {
IdString name = nets_by_udata.at(n)->name;
auto fnd = net_crit.find(name);
auto &net = nets.at(n);
net.max_crit = 0;
if (fnd == net_crit.end())
continue;
for (auto c : fnd->second.criticality)
net.max_crit = std::max(net.max_crit, c);
}
std::stable_sort(route_queue.begin(), route_queue.end(),
[&](int na, int nb) { return nets.at(na).max_crit > nets.at(nb).max_crit; });
}
#if 0
for (size_t j = 0; j < route_queue.size(); j++) {
route_net(st, nets_by_udata[route_queue[j]], false);