Improve performance of triplet finding

device/alpaka/src/seeding/seed_finding.cpp

@@ -24,6 +24,8 @@
 #include "traccc/seeding/device/count_triplets.hpp"
 #include "traccc/seeding/device/find_doublets.hpp"
 #include "traccc/seeding/device/find_triplets.hpp"
+#include "traccc/seeding/device/make_mid_bot_lincircles.hpp"
+#include "traccc/seeding/device/make_mid_top_lincircles.hpp"
 #include "traccc/seeding/device/reduce_triplet_counts.hpp"
 #include "traccc/seeding/device/select_seeds.hpp"
 #include "traccc/seeding/device/update_triplet_weights.hpp"
@@ -71,6 +73,42 @@ struct FindDoublets {
     }
 };
 
+// Kernel for running @c traccc::device::make_mid_bot_lincircles
+struct MakeMidBotLinCircles {
+    template <typename TAcc>
+    ALPAKA_FN_ACC void operator()(
+        TAcc const& acc,
+        device::device_doublet_collection_types::const_view mb_doublet_view,
+        device::doublet_counter_collection_types::const_view doublet_count_view,
+        edm::spacepoint_collection::const_view spacepoint_view,
+        traccc::details::spacepoint_grid_types::const_view sp_grid_view,
+        vecmem::data::vector_view<lin_circle> out_view) const {
+        auto const globalThreadIdx =
+            ::alpaka::getIdx<::alpaka::Grid, ::alpaka::Threads>(acc)[0u];
+        device::make_mid_bot_lincircles(globalThreadIdx, mb_doublet_view,
+                                        doublet_count_view, spacepoint_view,
+                                        sp_grid_view, out_view);
+    }
+};
+
+// Kernel for running @c traccc::device::make_mid_top_lincircles
+struct MakeMidTopLinCircles {
+    template <typename TAcc>
+    ALPAKA_FN_ACC void operator()(
+        TAcc const& acc,
+        device::device_doublet_collection_types::const_view mt_doublet_view,
+        device::doublet_counter_collection_types::const_view doublet_count_view,
+        edm::spacepoint_collection::const_view spacepoint_view,
+        traccc::details::spacepoint_grid_types::const_view sp_grid_view,
+        vecmem::data::vector_view<lin_circle> out_view) const {
+        auto const globalThreadIdx =
+            ::alpaka::getIdx<::alpaka::Grid, ::alpaka::Threads>(acc)[0u];
+        device::make_mid_top_lincircles(globalThreadIdx, mt_doublet_view,
+                                        doublet_count_view, spacepoint_view,
+                                        sp_grid_view, out_view);
+    }
+};
+
 // Kernel for running @c traccc::device::count_triplets
 struct CountTriplets {
     template <typename TAcc>
@@ -82,12 +120,15 @@ struct CountTriplets {
         device::device_doublet_collection_types::const_view mb_doublets,
         device::device_doublet_collection_types::const_view mt_doublets,
         device::triplet_counter_spM_collection_types::view spM_counter,
-        device::triplet_counter_collection_types::view midBot_counter) const {
+        device::triplet_counter_collection_types::view midBot_counter,
+        vecmem::data::vector_view<lin_circle> mb_circles,
+        vecmem::data::vector_view<lin_circle> mt_circles) const {
         auto const globalThreadIdx =
             ::alpaka::getIdx<::alpaka::Grid, ::alpaka::Threads>(acc)[0u];
         device::count_triplets(globalThreadIdx, config, spacepoints, sp_grid,
                                doublet_counter, mb_doublets, mt_doublets,
-                               spM_counter, midBot_counter);
+                               spM_counter, midBot_counter, mb_circles,
+                               mt_circles);
     }
 };
 
@@ -118,13 +159,16 @@ struct FindTriplets {
         device::device_doublet_collection_types::const_view mt_doublets,
         device::triplet_counter_spM_collection_types::const_view spM_tc,
         device::triplet_counter_collection_types::const_view midBot_tc,
+        vecmem::data::vector_view<lin_circle> mb_circles,
+        vecmem::data::vector_view<lin_circle> mt_circles,
         device::device_triplet_collection_types::view triplet_view) const {
 
         auto const globalThreadIdx =
             ::alpaka::getIdx<::alpaka::Grid, ::alpaka::Threads>(acc)[0u];
         device::find_triplets(globalThreadIdx, config, filter_config,
                               spacepoints, sp_grid, doublet_counter,
-                              mt_doublets, spM_tc, midBot_tc, triplet_view);
+                              mt_doublets, spM_tc, midBot_tc, mb_circles,
+                              mt_circles, triplet_view);
     }
 };
 
@@ -288,6 +332,37 @@ edm::seed_collection::buffer seed_finding::operator()(
                         vecmem::get_data(doublet_buffer_mb),
                         vecmem::get_data(doublet_buffer_mt));
 
+    vecmem::data::vector_buffer<lin_circle> mid_bot_lin_circles{
+        pBufHost_counter->m_nMidBot, m_mr.main};
+    m_copy.setup(mid_bot_lin_circles)->wait();
+    vecmem::data::vector_buffer<lin_circle> mid_top_lin_circles{
+        pBufHost_counter->m_nMidTop, m_mr.main};
+    m_copy.setup(mid_top_lin_circles)->wait();
+
+    {
+        const unsigned int n_threads = 128;
+        const unsigned int n_mid_bot_blocks =
+            (pBufHost_counter->m_nMidBot + n_threads - 1) / n_threads;
+        const unsigned int n_mid_top_blocks =
+            (pBufHost_counter->m_nMidTop + n_threads - 1) / n_threads;
+        const auto mid_bot_workdiv =
+            makeWorkDiv<Acc>(n_mid_bot_blocks, n_threads);
+        const auto mid_top_workdiv =
+            makeWorkDiv<Acc>(n_mid_top_blocks, n_threads);
+
+        ::alpaka::exec<Acc>(
+            queue, mid_bot_workdiv, kernels::MakeMidBotLinCircles{},
+            vecmem::get_data(doublet_buffer_mb),
+            vecmem::get_data(doublet_counter_buffer), spacepoints_view, g2_view,
+            vecmem::get_data(mid_bot_lin_circles));
+
+        ::alpaka::exec<Acc>(
+            queue, mid_top_workdiv, kernels::MakeMidTopLinCircles{},
+            vecmem::get_data(doublet_buffer_mb),
+            vecmem::get_data(doublet_counter_buffer), spacepoints_view, g2_view,
+            vecmem::get_data(mid_top_lin_circles));
+    }
+
     // Set up the triplet counter buffers
     device::triplet_counter_spM_collection_types::buffer
         triplet_counter_spM_buffer = {doublet_counter_buffer_size, m_mr.main};
@@ -311,7 +386,9 @@ edm::seed_collection::buffer seed_finding::operator()(
                         vecmem::get_data(doublet_buffer_mb),
                         vecmem::get_data(doublet_buffer_mt),
                         vecmem::get_data(triplet_counter_spM_buffer),
-                        vecmem::get_data(triplet_counter_midBot_buffer));
+                        vecmem::get_data(triplet_counter_midBot_buffer),
+                        vecmem::get_data(mid_bot_lin_circles),
+                        vecmem::get_data(mid_top_lin_circles));
 
     // Calculate the number of threads and thread blocks to run the triplet
     // count reduction kernel for.
@@ -353,6 +430,8 @@ edm::seed_collection::buffer seed_finding::operator()(
                         vecmem::get_data(doublet_buffer_mt),
                         vecmem::get_data(triplet_counter_spM_buffer),
                         vecmem::get_data(triplet_counter_midBot_buffer),
+                        vecmem::get_data(mid_bot_lin_circles),
+                        vecmem::get_data(mid_top_lin_circles),
                         vecmem::get_data(triplet_buffer));
 
     blocksPerGrid =

device/common/include/traccc/edm/device/triplet_counter.hpp

@@ -47,6 +47,9 @@ struct triplet_counter {
     /// The position in which these triplets will be added
     unsigned int posTriplets = 0;
 
+    /// Index of the bottom-middle doublet
+    unsigned int m_botMidIdx = 0;
+
 };  // struct triplet_counter
 
 /// Declare all triplet counter collection types

device/common/include/traccc/seeding/device/count_triplets.hpp

@@ -48,7 +48,9 @@ inline void count_triplets(
     const device_doublet_collection_types::const_view& mid_bot_doublet_view,
     const device_doublet_collection_types::const_view& mid_top_doublet_view,
     triplet_counter_spM_collection_types::view spM_tc,
-    triplet_counter_collection_types::view mb_tc);
+    triplet_counter_collection_types::view mb_tc,
+    vecmem::data::vector_view<const lin_circle> mid_bot_circles,
+    vecmem::data::vector_view<const lin_circle> mid_top_circles);
 
 }  // namespace traccc::device
 

device/common/include/traccc/seeding/device/find_triplets.hpp

@@ -49,6 +49,8 @@ inline void find_triplets(
     const device_doublet_collection_types::const_view& mid_top_doublet_view,
     const triplet_counter_spM_collection_types::const_view& spM_tc_view,
     const triplet_counter_collection_types::const_view& tc_view,
+    vecmem::data::vector_view<const lin_circle> mid_bot_circle_view,
+    vecmem::data::vector_view<const lin_circle> mid_top_circle_view,
     device_triplet_collection_types::view triplet_view);
 
 }  // namespace traccc::device

device/common/include/traccc/seeding/device/impl/count_triplets.ipp

@@ -24,7 +24,9 @@ inline void count_triplets(
     const device_doublet_collection_types::const_view& mid_bot_doublet_view,
     const device_doublet_collection_types::const_view& mid_top_doublet_view,
     triplet_counter_spM_collection_types::view spM_tc_view,
-    triplet_counter_collection_types::view mb_tc_view) {
+    triplet_counter_collection_types::view mb_tc_view,
+    vecmem::data::vector_view<const lin_circle> mid_bot_circle_view,
+    vecmem::data::vector_view<const lin_circle> mid_top_circle_view) {
 
     // Create device copy of input parameters
     const device_doublet_collection_types::const_device mid_bot_doublet_device(
@@ -43,6 +45,10 @@ inline void count_triplets(
     const device_doublet_collection_types::const_device mid_top_doublet_device(
         mid_top_doublet_view);
     const doublet_counter_collection_types::const_device dc_device(dc_view);
+    const vecmem::device_vector<const lin_circle> mid_bot_circles(
+        mid_bot_circle_view);
+    const vecmem::device_vector<const lin_circle> mid_top_circles(
+        mid_top_circle_view);
 
     // Create device copy of output parameterss
     triplet_counter_collection_types::device mb_triplet_counter(mb_tc_view);
@@ -61,24 +67,16 @@ inline void count_triplets(
     const edm::spacepoint_collection::const_device::const_proxy_type spM =
         spacepoints.at(sp_device.bin(spM_loc.bin_idx)[spM_loc.sp_idx]);
     const sp_location spB_loc = mid_bot.sp2;
-    // bottom spacepoint
-    const edm::spacepoint_collection::const_device::const_proxy_type spB =
-        spacepoints.at(sp_device.bin(spB_loc.bin_idx)[spB_loc.sp_idx]);
 
     // Apply the conformal transformation to middle-bot doublet
-    traccc::lin_circle lb = doublet_finding_helper::transform_coordinates<
-        details::spacepoint_type::bottom>(spM, spB);
+    const traccc::lin_circle lb = mid_bot_circles.at(globalIndex);
 
     // Calculate some physical quantities required for triplet compatibility
     // check
     scalar iSinTheta2 = static_cast<scalar>(1.) + lb.cotTheta() * lb.cotTheta();
     scalar scatteringInRegion2 = config.maxScatteringAngle2 * iSinTheta2;
     scatteringInRegion2 *= config.sigmaScattering * config.sigmaScattering;
 
-    // These two quantities are used as output parameters in
-    // triplet_finding_helper::isCompatible but their values are irrelevant
-    scalar curvature, impact_parameter;
-
     // find the reference (start) index of the mid-top doublet container
     // item vector, where the doublets are recorded
     const unsigned int mt_start_idx = doublet_counts.m_posMidTop;
@@ -87,18 +85,16 @@ inline void count_triplets(
     // number of triplets per middle-bot doublet
     unsigned int num_triplets_per_mb = 0;
 
-    // iterate over mid-top doublets
-    for (unsigned int i = mt_start_idx; i < mt_end_idx; ++i) {
-        const traccc::sp_location spT_loc = mid_top_doublet_device[i].sp2;
-
-        const edm::spacepoint_collection::const_device::const_proxy_type spT =
-            spacepoints.at(sp_device.bin(spT_loc.bin_idx)[spT_loc.sp_idx]);
+    const unsigned int num_mt = mt_end_idx - mt_start_idx;
 
+    // iterate over mid-top doublets
+    for (unsigned int ri = 0; ri < num_mt; ++ri) {
         // Apply the conformal transformation to middle-top doublet
-        traccc::lin_circle lt = doublet_finding_helper::transform_coordinates<
-            details::spacepoint_type::top>(spM, spT);
+        const lin_circle& lt = mid_top_circles.at(ri + mt_start_idx);
 
-        // Check if mid-bot and mid-top doublets can form a triplet
+        // These two quantities are used as output parameters in
+        // triplet_finding_helper::isCompatible but their values are irrelevant
+        scalar curvature, impact_parameter;
         if (triplet_finding_helper::isCompatible(
                 spM, lb, lt, config, iSinTheta2, scatteringInRegion2, curvature,
                 impact_parameter)) {
@@ -114,8 +110,9 @@ inline void count_triplets(
         const unsigned int posTriplets =
             nTriplets.fetch_add(num_triplets_per_mb);
 
-        mb_triplet_counter.push_back(
-            {spB_loc, counter_link, num_triplets_per_mb, posTriplets});
+        mb_triplet_counter.push_back({spB_loc, counter_link,
+                                      num_triplets_per_mb, posTriplets,
+                                      globalIndex});
     }
 }
 

device/common/include/traccc/seeding/device/impl/find_triplets.ipp

@@ -25,6 +25,8 @@ inline void find_triplets(
     const device_doublet_collection_types::const_view& mid_top_doublet_view,
     const triplet_counter_spM_collection_types::const_view& spM_tc_view,
     const triplet_counter_collection_types::const_view& tc_view,
+    vecmem::data::vector_view<const lin_circle> mid_bot_circle_view,
+    vecmem::data::vector_view<const lin_circle> mid_top_circle_view,
     device_triplet_collection_types::view triplet_view) {
 
     // Check if anything needs to be done.
@@ -44,6 +46,10 @@ inline void find_triplets(
     const traccc::details::spacepoint_grid_types::const_device sp_grid(sp_view);
     const triplet_counter_spM_collection_types::const_device triplet_counts_spM(
         spM_tc_view);
+    const vecmem::device_vector<const lin_circle> mid_bot_circles(
+        mid_bot_circle_view);
+    const vecmem::device_vector<const lin_circle> mid_top_circles(
+        mid_top_circle_view);
 
     // Get the current work item information
     const triplet_counter mid_bot_counter = triplet_counts.at(globalIndex);
@@ -69,8 +75,8 @@ inline void find_triplets(
     device_triplet_collection_types::device triplets(triplet_view);
 
     // Apply the conformal transformation to middle-bot doublet
-    const traccc::lin_circle lb = doublet_finding_helper::transform_coordinates<
-        details::spacepoint_type::bottom>(spM, spB);
+    const traccc::lin_circle lb =
+        mid_bot_circles.at(mid_bot_counter.m_botMidIdx);
 
     // Calculate some physical quantities required for triplet compatibility
     // check
@@ -79,10 +85,6 @@ inline void find_triplets(
                                        config.sigmaScattering *
                                        config.sigmaScattering;
 
-    // These two quantities are used as output parameters in
-    // triplet_finding_helper::isCompatible but their values are irrelevant
-    scalar curvature, impact_parameter;
-
     // find the reference (start) index of the mid-top doublet collection
     // item vector, where the doublets are recorded
     const unsigned int mt_start_idx = doublet_count.m_posMidTop;
@@ -95,19 +97,15 @@ inline void find_triplets(
 
     // iterate over mid-top doublets
     for (unsigned int i = mt_start_idx; i < mt_end_idx; ++i) {
-        const sp_location spT_loc = mid_top_doublet_device[i].sp2;
+        // Apply the conformal transformation to middle-top doublet
+        const traccc::lin_circle& lt = mid_top_circles.at(i);
 
+        const sp_location spT_loc = mid_top_doublet_device[i].sp2;
         const unsigned int spT_idx =
             sp_grid.bin(spT_loc.bin_idx)[spT_loc.sp_idx];
-        const edm::spacepoint_collection::const_device::const_proxy_type spT =
-            spacepoints.at(spT_idx);
-
-        // Apply the conformal transformation to middle-top doublet
-        const traccc::lin_circle lt =
-            doublet_finding_helper::transform_coordinates<
-                details::spacepoint_type::top>(spM, spT);
 
         // Check if mid-bot and mid-top doublets can form a triplet
+        scalar curvature, impact_parameter;
         if (triplet_finding_helper::isCompatible(
                 spM, lb, lt, config, iSinTheta2, scatteringInRegion2, curvature,
                 impact_parameter)) {

device/common/include/traccc/seeding/device/make_mid_bot_lincircles.hpp

@@ -0,0 +1,48 @@
+/** TRACCC library, part of the ACTS project (R&D line)
+ *
+ * (c) 2025 CERN for the benefit of the ACTS project
+ *
+ * Mozilla Public License Version 2.0
+ */
+
+#pragma once
+
+namespace traccc::device {
+/**
+ * @brief Kernel to create middle-bottom linearised circles.
+ */
+TRACCC_HOST_DEVICE
+inline void make_mid_bot_lincircles(
+    global_index_t tid,
+    device::device_doublet_collection_types::const_view mb_doublet_view,
+    device::doublet_counter_collection_types::const_view doublet_count_view,
+    edm::spacepoint_collection::const_view spacepoint_view,
+    traccc::details::spacepoint_grid_types::const_view sp_grid_view,
+    vecmem::data::vector_view<lin_circle> out_view) {
+
+    const device::device_doublet_collection_types::const_device doublets(
+        mb_doublet_view);
+    const device::doublet_counter_collection_types::const_device doublet_counts(
+        doublet_count_view);
+    const edm::spacepoint_collection::const_device spacepoints(spacepoint_view);
+    traccc::details::spacepoint_grid_types::const_device sp_grid(sp_grid_view);
+    vecmem::device_vector<lin_circle> out(out_view);
+
+    if (tid >= doublets.size()) {
+        return;
+    }
+
+    const device::device_doublet dub = doublets.at(tid);
+    const unsigned int counter_link = dub.counter_link;
+    const device::doublet_counter count = doublet_counts.at(counter_link);
+    const sp_location spM_loc = count.m_spM;
+    const edm::spacepoint_collection::const_device::const_proxy_type spM =
+        spacepoints.at(sp_grid.bin(spM_loc.bin_idx)[spM_loc.sp_idx]);
+    const sp_location spB_loc = dub.sp2;
+    const edm::spacepoint_collection::const_device::const_proxy_type spB =
+        spacepoints.at(sp_grid.bin(spB_loc.bin_idx)[spB_loc.sp_idx]);
+
+    out.at(tid) = doublet_finding_helper::transform_coordinates<
+        traccc::details::spacepoint_type::bottom>(spM, spB);
+}
+}  // namespace traccc::device