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Merge pull request #2462 from verilog-to-routing/debug_6d_router_look…
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…ahead

Debug Router Lookahead For 3D Architecture
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@vaughnbetz
vaughnbetz committed Dec 7, 2023
2 parents 438b573 + 6f86b2d commit c498f81
Showing 1 changed file with 58 additions and 51 deletions.
109 changes: 58 additions & 51 deletions vpr/src/route/router_lookahead_map.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -265,7 +265,7 @@ static void min_global_cost_map(vtr::NdMatrix<util::Cost_Entry, 3>& internal_opi
* @param delta_y
* @return (delay, congestion)
*/
static std::pair<float, float> get_cost_from_src_opin(const std::map<int, util::t_reachable_wire_inf>& src_opin_delay_map,
static std::pair<float, float> get_cost_from_src_opin(const std::vector<std::map<int, util::t_reachable_wire_inf>>& src_opin_delay_map,
int delta_x,
int delta_y,
int to_layer_num);
Expand Down Expand Up @@ -471,7 +471,7 @@ std::pair<float, float> MapLookahead::get_expected_delay_and_cong(RRNodeId from_

auto from_ptc = rr_graph.node_ptc_num(from_node);

std::tie(expected_delay_cost, expected_cong_cost) = get_cost_from_src_opin(src_opin_delays[from_layer_num][from_tile_index][from_ptc][to_layer_num],
std::tie(expected_delay_cost, expected_cong_cost) = get_cost_from_src_opin(src_opin_delays[from_layer_num][from_tile_index][from_ptc],
delta_x,
delta_y,
to_layer_num);
Expand Down Expand Up @@ -1490,63 +1490,70 @@ static void min_global_cost_map(vtr::NdMatrix<util::Cost_Entry, 3>& internal_opi
}
}

static std::pair<float, float> get_cost_from_src_opin(const std::map<int, util::t_reachable_wire_inf>& src_opin_delay_map,
static std::pair<float, float> get_cost_from_src_opin(const std::vector<std::map<int, util::t_reachable_wire_inf>>& src_opin_delay_map,
int delta_x,
int delta_y,
int to_layer_num) {
float expected_delay_cost = std::numeric_limits<float>::infinity();
float expected_cong_cost = std::numeric_limits<float>::infinity();
if (src_opin_delay_map.empty()) {
//During lookahead profiling we were unable to find any wires which connected
//to this PTC.
//
//This can sometimes occur at very low channel widths (e.g. during min W search on
//small designs) where W discretization combined with fraction Fc may cause some
//pins/sources to be left disconnected.
//
//Such RR graphs are of course unroutable, but that should be determined by the
//router. So just return an arbitrary value here rather than error.

//We choose to return the largest (non-infinite) value possible, but scaled
//down by a large factor to maintain some dynaimc range in case this value ends
//up being processed (e.g. by the timing analyzer).
//
//The cost estimate should still be *extremely* large compared to a typical delay, and
//so should ensure that the router de-prioritizes exploring this path, but does not
//forbid the router from trying.
expected_delay_cost = std::numeric_limits<float>::max() / 1e12;
expected_cong_cost = std::numeric_limits<float>::max() / 1e12;
} else {
//From the current SOURCE/OPIN we look-up the wiretypes which are reachable
//and then add the estimates from those wire types for the distance of interest.
//If there are multiple options we use the minimum value.
for (const auto& kv : src_opin_delay_map) {
const util::t_reachable_wire_inf& reachable_wire_inf = kv.second;

Cost_Entry wire_cost_entry;
if (reachable_wire_inf.wire_rr_type == SINK) {
//Some pins maybe reachable via a direct (OPIN -> IPIN) connection.
//In the lookahead, we treat such connections as 'special' wire types
//with no delay/congestion cost
wire_cost_entry.delay = 0;
wire_cost_entry.congestion = 0;
} else {
//For an actual accessible wire, we query the wire look-up to get it's
//delay and congestion cost estimates
wire_cost_entry = get_wire_cost_entry(reachable_wire_inf.wire_rr_type,
reachable_wire_inf.wire_seg_index,
reachable_wire_inf.layer_number,
delta_x,
delta_y,
to_layer_num);
}

float this_delay_cost = reachable_wire_inf.delay + wire_cost_entry.delay;
float this_cong_cost = reachable_wire_inf.congestion + wire_cost_entry.congestion;
for (const auto& layer_src_opin_delay_map : src_opin_delay_map) {
float layer_expected_delay_cost = std::numeric_limits<float>::infinity();
float layer_expected_cong_cost = std::numeric_limits<float>::infinity();
if (layer_src_opin_delay_map.empty()) {
//During lookahead profiling we were unable to find any wires which connected
//to this PTC.
//
//This can sometimes occur at very low channel widths (e.g. during min W search on
//small designs) where W discretization combined with fraction Fc may cause some
//pins/sources to be left disconnected.
//
//Such RR graphs are of course unroutable, but that should be determined by the
//router. So just return an arbitrary value here rather than error.

//We choose to return the largest (non-infinite) value possible, but scaled
//down by a large factor to maintain some dynaimc range in case this value ends
//up being processed (e.g. by the timing analyzer).
//
//The cost estimate should still be *extremely* large compared to a typical delay, and
//so should ensure that the router de-prioritizes exploring this path, but does not
//forbid the router from trying.
layer_expected_delay_cost = std::numeric_limits<float>::max() / 1e12;
layer_expected_cong_cost = std::numeric_limits<float>::max() / 1e12;
} else {
//From the current SOURCE/OPIN we look-up the wiretypes which are reachable
//and then add the estimates from those wire types for the distance of interest.
//If there are multiple options we use the minimum value.
for (const auto& kv : layer_src_opin_delay_map) {
const util::t_reachable_wire_inf& reachable_wire_inf = kv.second;

Cost_Entry wire_cost_entry;
if (reachable_wire_inf.wire_rr_type == SINK) {
//Some pins maybe reachable via a direct (OPIN -> IPIN) connection.
//In the lookahead, we treat such connections as 'special' wire types
//with no delay/congestion cost
wire_cost_entry.delay = 0;
wire_cost_entry.congestion = 0;
} else {
//For an actual accessible wire, we query the wire look-up to get it's
//delay and congestion cost estimates
wire_cost_entry = get_wire_cost_entry(reachable_wire_inf.wire_rr_type,
reachable_wire_inf.wire_seg_index,
reachable_wire_inf.layer_number,
delta_x,
delta_y,
to_layer_num);
}

float this_delay_cost = reachable_wire_inf.delay + wire_cost_entry.delay;
float this_cong_cost = reachable_wire_inf.congestion + wire_cost_entry.congestion;

expected_delay_cost = std::min(expected_delay_cost, this_delay_cost);
expected_cong_cost = std::min(expected_cong_cost, this_cong_cost);
layer_expected_delay_cost = std::min(layer_expected_delay_cost, this_delay_cost);
layer_expected_cong_cost = std::min(layer_expected_cong_cost, this_cong_cost);
}
}
expected_delay_cost = std::min(expected_delay_cost, layer_expected_delay_cost);
expected_cong_cost = std::min(expected_cong_cost, layer_expected_cong_cost);
}

return std::make_pair(expected_delay_cost, expected_cong_cost);
Expand Down

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