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Browse / github.com/storytold/effectcraft / patch
Camera tracking: keep bundle-adjustment Jacobians on the stack
camtrack: bundle adjustment allocates a Vec per point and iteration (-7.6 %) ## Problem `camtrack/bundle.rs:209` (with `cam_jac`, `:147`): a new `Vec::with_capacity(8)` per point and per outer LM iteration, also for motion-only refinement of a single frame. In the full mode up to nine entries are needed, so the vector can even grow. ## Proposal A local fixed array with a counter (capacity ten in the prototype), same push and iteration order; define the maximum entry count in one place so future parameters cannot cause an array panic. ## Measured (prototype) 300 single-camera BA calls: 1.334 G -> 1.233 G instructions (-7.6 %, 1.08x), 134.4 -> 130.3 ms. Hashes identica
- Status
- open
- Score
- 0.00
- Adopters
- 0 other operators
- Author
- vangel76 (imported from pull request #2340, open)
- Base
991904888a20b7da72b2a4880b21c7d912154736- Size
- +70 −5 in 1 file
- Review
- pending
- Shared
- 2026-10-28
- Id
a0b39231bebf49dd21b7cfda
How it went
No other operator has reported using it yet.
Diff
raw · crates/track/src/camtrack/bundle.rs
@@ -147,8 +147,52 @@ fn layout(ncam: usize, o: &BaOpts) -> Layout { Layout { start, fidx, shared, dist, n, rot_only: o.fix_centers } } +// Six pose parameters, one shared OR per-camera focal parameter, two distortion parameters.+const MAX_CAMERA_JACOBIAN_ENTRIES: usize = 6 + 1 + 2;+type CameraJacobianEntry = (usize, [f64; 2]);++/// Keeps the current parameter set on the stack. Extra parameters spill rather than panic+/// if a future extension grows beyond the inline capacity.+struct CameraJacobian {+ entries: [CameraJacobianEntry; MAX_CAMERA_JACOBIAN_ENTRIES],+ len: usize,+ overflow: Vec<CameraJacobianEntry>,+}++impl CameraJacobian {+ fn new() -> Self {+ Self { entries: [(0, [0.0; 2]); MAX_CAMERA_JACOBIAN_ENTRIES], len: 0, overflow: Vec::new() }+ }++ fn clear(&mut self) {+ self.len = 0;+ self.overflow.clear();+ }++ fn push(&mut self, entry: CameraJacobianEntry) {+ if self.overflow.is_empty() {+ if let Some(slot) = self.entries.get_mut(self.len) {+ *slot = entry;+ self.len += 1;+ return;+ }+ self.overflow.extend_from_slice(&self.entries);+ }+ self.overflow.push(entry);+ }++ fn as_slice(&self) -> &[CameraJacobianEntry] {+ if self.overflow.is_empty() {+ // len only grows after a successful get_mut, so it cannot exceed capacity.+ self.entries.get(..self.len).unwrap_or_default()+ } else {+ &self.overflow+ }+ }+}+ /// Camera-side Jacobian entries of one observation: (parameter index, d r / d param).-fn cam_jac(l: &Layout, ci: usize, c: &BaCam, xc: V3, a: &[[f64; 3]; 2], p: [f64; 2], out: &mut Vec<(usize, [f64; 2])>) {+fn cam_jac(l: &Layout, ci: usize, c: &BaCam, xc: V3, a: &[[f64; 3]; 2], p: [f64; 2], out: &mut CameraJacobian) { out.clear(); let s = l.start[ci]; if s != usize::MAX {@@ -206,7 +250,7 @@ pub fn adjust(cams: &mut [BaCam], pts: &mut [V3], obs: &[BaObs], o: &BaOpts) -> } let build_point = |j: usize, s_acc: &mut Vec<f64>, bc: &mut Vec<f64>| -> PtSys { let mut ps = PtSys { v: [[0.0; 3]; 3], bp: [0.0; 3], w: vec![] };- let mut jc: Vec<(usize, [f64; 2])> = Vec::with_capacity(8);+ let mut jc = CameraJacobian::new(); for &oi in &by_pt[j] { let ob = &obs[oi as usize]; let ci = ob.cam as usize;@@ -231,6 +275,7 @@ pub fn adjust(cams: &mut [BaCam], pts: &mut [V3], obs: &[BaObs], o: &BaOpts) -> jc.push((g, [dk[0][0], dk[1][0]])); jc.push((g + 1, [dk[0][1], dk[1][1]])); }+ let jc = jc.as_slice(); // Point Jacobian: A R. let jx = if o.fix_points { [[0.0; 3]; 2]@@ -239,9 +284,9 @@ pub fn adjust(cams: &mut [BaCam], pts: &mut [V3], obs: &[BaObs], o: &BaOpts) -> let r1 = mtv(&c.pose.r, a[1]); [r0, r1] };- for (ia, ja) in &jc {+ for (ia, ja) in jc.iter() { bc[*ia] -= w * (ja[0] * r[0] + ja[1] * r[1]);- for (ib, jb) in &jc {+ for (ib, jb) in jc.iter() { s_acc[ia * n + ib] += w * (ja[0] * jb[0] + ja[1] * jb[1]); } }@@ -252,7 +297,7 @@ pub fn adjust(cams: &mut [BaCam], pts: &mut [V3], obs: &[BaObs], o: &BaOpts) -> ps.v[a1][b1] += w * (jx[0][a1] * jx[0][b1] + jx[1][a1] * jx[1][b1]); } }- for (ia, ja) in &jc {+ for (ia, ja) in jc.iter() { let wv = [w * (ja[0] * jx[0][0] + ja[1] * jx[1][0]), w * (ja[0] * jx[0][1] + ja[1] * jx[1][1]), w * (ja[0] * jx[0][2] + ja[1] * jx[1][2])]; // Each observation of a point is on another camera: only the shared focal@@ -464,6 +509,26 @@ mod tests { use super::*; use crate::camtrack::geometry::Rng; + #[test]+ fn camera_jacobian_keeps_extra_parameters_and_resets() {+ let mut jac = CameraJacobian::new();+ let count = MAX_CAMERA_JACOBIAN_ENTRIES + 3;+ for i in 0..count {+ jac.push((i, [i as f64, -(i as f64)]));+ }+ assert_eq!(jac.as_slice().iter().count(), count);+ for (i, entry) in jac.as_slice().iter().enumerate() {+ assert_eq!(*entry, (i, [i as f64, -(i as f64)]));+ }+ jac.clear();+ assert_eq!(jac.as_slice().iter().count(), 0);+ for i in 0..MAX_CAMERA_JACOBIAN_ENTRIES {+ jac.push((i, [1.0, 2.0]));+ }+ assert_eq!(jac.as_slice().iter().count(), MAX_CAMERA_JACOBIAN_ENTRIES);+ assert!(jac.overflow.is_empty());+ }+ #[test] fn bundle_adjustment_converges_from_noise() { let mut rng = Rng(99);