HLT1 UT-related tracking updates

• Introduction
• 0. Legacy code cleanup and new features
• 1. New UT Decoding
  • New layout
  • Throughput improvement
• 2. New CompassUT
  • Performance improvement
• 3. New Downstream Tracking
  • Performance improvement
• 4. Adaptive Thresholds for Hardcoded Limits
• Throughput in MEPs data

Introduction

This MR includes five different sets of changes, each grouped into a separate Git commit. It is recommended to review the commits individually.

Needs lhcb-datapkg/ParamFiles!127 (merged)

FYI: @adeoyang @bjashal @vsvintoz @vkholoim @dovombru @mveghel @cagapopo @gligorov (Feel free to tag additional people as needed )

0. Legacy code cleanup and new features

• Remove unused dumpers (downstream track and downstream composite).
• Remove the unused TrackMatchingConsts::MagnetParametrization.
• Add a new helper, LinearAlgebra.cuh, for SolveCholesky<N>.
• Add make_short2 in the CPU backend.

1. New UT Decoding

• Change the UT hits container layout from x-based sector groups to y-based sector groups.
• Implement new UT decoding, mapping each thread to a cluster.
• Adapt matching and downstream tracking to the new UT hits layout.

Presented in WP2

New layout

Throughput improvement

2. New CompassUT

• Implement a new CompassUT using the updated UT hits layout.

Presented in WP2

Performance improvement

3. New Downstream Tracking

• Implement new Downstream tracking, replacing the (0,0) assumption with a general triplet search.

Presented in WP2

Performance improvement

4. Adaptive Thresholds for Hardcoded Limits

• Add adaptive thresholds and proper counters in Matching.
• Add adaptive thresholds and proper counters in Downstream.

The event will be reconstructed up to N times (default = 2): when it exceeds the hardcoded container limit, the search window size is scaled down by half, and the event is reprocessed.

Throughput in MEPs data

backend/include/CPUBackend.h

@@ -126,6 +126,13 @@ struct short2 {
   short y;
 };
 
+inline short2 make_short2(short x, short y)
+{
+  short2 out;
+  out.x = x;
+  out.y = y;
+  return out;
+}
 struct float3 {
   float x;
   float y;