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Some cleanups in qwp

This commit is contained in:
Clifford Wolf 2015-09-26 10:42:27 +02:00
parent ddcfc99f8c
commit 281c1f4029
1 changed files with 16 additions and 7 deletions
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23
passes/cmds/qwp.cc
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@ -203,8 +203,8 @@ struct QwpWorker
void solve(bool alt_mode = false) void solve(bool alt_mode = false)
{ {
// A := observation_matrix // A := constraint_matrix
// y := observation_rhs_vector // y := constraint_rhs_vector
// //
// AA = A' * A // AA = A' * A
// Ay = A' * y // Ay = A' * y
@ -215,6 +215,10 @@ struct QwpWorker
int N = GetSize(nodes), N1 = N+1; int N = GetSize(nodes), N1 = N+1;
vector<double> M(N * N1); vector<double> M(N * N1);
// Edge constraints:
// A[i,:] := [ 0 0 .... 0 weight 0 ... 0 -weight 0 ... 0 0], y[i] := 0
//
// i.e. nonzero columns in A[i,:] at the two node indices.
for (auto &edge : edges) for (auto &edge : edges)
{ {
int idx1 = edge.first.first; int idx1 = edge.first.first;
@ -228,6 +232,14 @@ struct QwpWorker
M[idx2 + idx1*N1] += -weight * weight; M[idx2 + idx1*N1] += -weight * weight;
} }
// Node constraints:
// A[i,:] := [ 0 0 .... 0 weight 0 ... 0 0], y[i] := weight * pos
//
// i.e. nonzero column in A[i,:] at the node index
//
// "tied" nodes have a large weight, pinning them in position. Untied
// nodes have a small weight, giving then a tiny preference to stay at
// the current position, making sure that AA never is singular.
for (int idx = 0; idx < GetSize(nodes); idx++) for (int idx = 0; idx < GetSize(nodes); idx++)
{ {
auto &node = nodes[idx]; auto &node = nodes[idx];
@ -453,7 +465,7 @@ struct QwpWorker
config.dump_file << stringf("</svg>\n"); config.dump_file << stringf("</svg>\n");
} }
void run_worker(int indent, bool return_after_solve = false) void run_worker(int indent)
{ {
int count_cells = 0; int count_cells = 0;
@ -481,9 +493,6 @@ struct QwpWorker
solve(); solve();
solve(true); solve(true);
if (return_after_solve)
return;
// detect median position and check for break condition // detect median position and check for break condition
vector<pair<double, int>> sorted_pos; vector<pair<double, int>> sorted_pos;
@ -769,7 +778,7 @@ struct QwpPass : public Pass {
log(" -dump <html_file_name>\n"); log(" -dump <html_file_name>\n");
log(" Dump a protocol of the placement algorithm to the html file.\n"); log(" Dump a protocol of the placement algorithm to the html file.\n");
log("\n"); log("\n");
log("Note: This implementation of a quadratic wirelength placer uses unoptimized\n"); log("Note: This implementation of a quadratic wirelength placer uses exact\n");
log("dense matrix operations. It is only a toy-placer for small circuits.\n"); log("dense matrix operations. It is only a toy-placer for small circuits.\n");
log("\n"); log("\n");
} }