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Changed the random number generator in packer to deterministic vtr::irand #2871

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Jan 28, 2025
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15 changes: 4 additions & 11 deletions vpr/src/pack/greedy_candidate_selector.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,8 @@ GreedyCandidateSelector::GreedyCandidateSelector(
is_clock_(is_clock),
is_global_(is_global),
net_output_feeds_driving_block_input_(net_output_feeds_driving_block_input),
timing_info_(timing_info) {
timing_info_(timing_info),
rng_(0) {
// Initialize the list of molecules to pack, the clustering data, and the
// net info.

Expand Down Expand Up @@ -779,17 +780,9 @@ void GreedyCandidateSelector::add_cluster_molecule_candidates_by_attraction_grou
return;
}

int min = 0;
int max = num_available_atoms - 1;

for (int j = 0; j < attraction_group_num_atoms_threshold_; j++) {
// FIXME: This is a non-deterministic random number generator and it is
// overkill to what this needs to be. Should use vtr::irand which
// would be faster.
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<> distr(min, max);
int selected_atom = distr(gen);
//Get a random atom between 0 and the number of available atoms - 1
int selected_atom = rng_.irand(num_available_atoms - 1);

AtomBlockId blk_id = available_atoms[selected_atom];

Expand Down
6 changes: 6 additions & 0 deletions vpr/src/pack/greedy_candidate_selector.h
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#include "cluster_legalizer.h"
#include "physical_types.h"
#include "vtr_vector.h"
#include "vtr_random.h"

// Forward declarations
class AtomNetlist;
Expand Down Expand Up @@ -516,5 +517,10 @@ class GreedyCandidateSelector {
/// @brief A count on the number of unrelated clustering attempts which
/// have been performed.
int num_unrelated_clustering_attempts_ = 0;

/// @brief Random number generator used by the clusterer. Currently this
/// is used only when selecting atoms from attraction groups, but
/// could be used for other purposes in the future.
vtr::RngContainer rng_;
};

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