From 4c3c017f7aac58df9574088b6bbf775729a64a3b Mon Sep 17 00:00:00 2001 From: dsengupta0628 Date: Wed, 12 Aug 2026 15:23:10 +0000 Subject: [PATCH] dcalc: reserve per column slack in PrimaDelayCalc::stampEqns Signed-off-by: dsengupta0628 --- dcalc/PrimaDelayCalc.cc | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/dcalc/PrimaDelayCalc.cc b/dcalc/PrimaDelayCalc.cc index a5ea608c..a23d417f 100644 --- a/dcalc/PrimaDelayCalc.cc +++ b/dcalc/PrimaDelayCalc.cc @@ -590,6 +590,17 @@ PrimaDelayCalc::stampEqns() C_.setZero(); B_.setZero(); + // The stamps below insert into G_/C_ in parasitic traversal order, which is + // unrelated to the node indices assigned by findNodeCount(). coeffRef() on a + // packed sparse column has no free slot for an out of order insert, so it + // shifts the remaining values over, making stampEqns() quadratic in the node + // count. Reserving slack per column gives the inserts somewhere to land. + // Node degree in an RC network is small; stamp_slack covers the diagonal, the + // resistor and coupling capacitor off diagonals and the driver row. + constexpr int stamp_slack = 8; + G_.reserve(Eigen::VectorXi::Constant(order_, stamp_slack)); + C_.reserve(Eigen::VectorXi::Constant(order_, stamp_slack)); + NetSet drvr_nets(network_); for (ArcDcalcArg &dcalc_arg : *dcalc_args_) { const Net *net = dcalc_arg.drvrNet(network_);