Prune commentary and stale Rust port notes
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@@ -1,51 +1,17 @@
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//! What each GPU arena costs to upload per frame, at layer 1 (docs/RUST.md's
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//! "Three test layers") -- the real transcript screen over the real bench
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//! fixture, with no window, no compositor and no GPU.
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//!
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//! cargo test --release --test arena_churn -- --ignored --nocapture
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//!
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//! from `scripts/rigs/ui-profile/`.
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//!
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//! It exists because the upload is the one part of a frame that layer 1
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//! *builds* and never performs, so `frame_profile.rs` cannot see it at
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//! all: the emulator's `stream: build p50` stayed at 10.5ms across a
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//! change that nearly halved layer 1's CPU frame, and nothing could say
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//! why until this could count bytes.
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//!
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//! Three numbers per array per frame, which is the point of the rig --
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//! any two of them alone are misleading:
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//!
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//! - **changed** is the floor: entries whose bytes actually differ from
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//! the previous frame, found by diffing. Nothing correct can upload
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//! less.
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//! - **uploaded** is what `iris` really writes, read from the same
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//! `Dirty` sets `UiRenderNode::update` consumes and cleared here the
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//! way an upload would clear them. Above `changed` by whatever the
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//! marking over-marks plus whatever range coalescing pulls in.
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//! - **whole** is what the old code wrote every time anything changed.
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//!
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//! `#[ignore]`d and assertion-free: it prints distributions, so
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//! `run-tests.sh` neither runs it nor can fail on it.
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use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
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use iris::harness::Harness;
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use iris::prelude::{GlyphPrimitive, Primitive, RectPrimitive};
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use iris::widget::Scrollable;
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use ui_profile::stats::pct_u64;
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/// Passes over the same content, alternating direction -- the same
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/// out-and-back `frame_profile.rs`'s fling drives, so the two rigs
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/// describe the same gesture.
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const PASSES: usize = 8;
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const VELOCITY: f32 = 12_000.0;
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const PASS_CAP_MS: u64 = 4_000;
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/// One array's per-frame totals.
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#[derive(Default)]
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struct Tally {
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name: &'static str,
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stride: usize,
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/// The previous frame's bytes, for the diff that finds the floor.
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prev: Vec<u8>,
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changed: Vec<u64>,
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uploaded: Vec<u64>,
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@@ -62,7 +28,6 @@ impl Tally {
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}
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}
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/// Records one frame, and clears the dirty set as an upload would.
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fn frame(&mut self, bytes: &[u8], ranges: Vec<std::ops::Range<usize>>) {
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let n = self.prev.len().min(bytes.len()) / self.stride;
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let mut changed = (0..n)
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@@ -71,8 +36,6 @@ impl Tally {
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self.prev[r.clone()] != bytes[r]
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})
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.count();
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// Everything past the old end is new, and so is dirty by
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// definition.
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changed += bytes.len() / self.stride - n;
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self.changed.push((changed * self.stride) as u64);
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self.uploaded
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@@ -85,11 +48,8 @@ impl Tally {
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fn report(&mut self) {
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let sum = |v: &[u64]| v.iter().sum::<u64>();
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let (changed, uploaded, whole) = (
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sum(&self.changed),
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sum(&self.uploaded),
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sum(&self.whole),
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);
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let (changed, uploaded, whole) =
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(sum(&self.changed), sum(&self.uploaded), sum(&self.whole));
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println!(
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" {:<10} whole {:>7.1} MB | uploaded {:>7.1} MB ({:>5.1}%) | floor {:>7.1} MB ({:>5.1}%)",
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self.name,
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@@ -114,9 +74,6 @@ impl Tally {
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}
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}
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/// The three arenas a transcript frame writes. Masks and move offsets are
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/// left out deliberately: they are a hundred-odd entries, so their whole
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/// buffer is smaller than one range of any of these.
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struct Arenas {
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instances: Tally,
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rects: Tally,
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@@ -132,15 +89,11 @@ impl Arenas {
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}
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}
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/// Reads this frame's dirty ranges out of the render state and clears
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/// them, exactly as `UiRenderNode::update` would on a real backend.
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fn frame(&mut self, h: &mut Harness) {
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let count = h.render.primitives.instances().len();
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let (entries, dirty) = h.render.primitives.instances_for_upload();
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// `PrimitiveInstance` is not exported, so the stride comes from
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// the slice rather than from `size_of`.
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let bytes: Vec<u8> = bytemuck::cast_slice(entries).to_vec();
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self.instances.stride = if count == 0 { 48 } else { bytes.len() / count };
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self.instances.stride = bytes.len().checked_div(count).unwrap_or(48);
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let ranges = dirty.ranges(count, 1024 / self.instances.stride);
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dirty.clear();
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self.instances.frame(&bytes, ranges);
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@@ -196,7 +149,6 @@ fn what_a_fling_uploads() {
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break;
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}
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}
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// A moment at rest between passes, as a finger would leave.
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t += 200;
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}
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println!("\na fling, {PASSES} passes:");
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@@ -1,44 +1,11 @@
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//! Profiling runs rather than tests: what a frame costs on the CPU, at
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//! layer 1 (docs/RUST.md's "Three test layers") -- the real
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//! transcript screen over the real bench fixture, with no window, no
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//! compositor and no GPU, on a clock this file owns. It exists so "the
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//! fling stutters" can be attributed rather than guessed at, and it is
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//! kept between investigations rather than rewritten each time (Iris,
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//! 2026-09-09: "please keep the profiling rig around for future use").
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//!
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//! cargo test --release --test frame_profile -- --ignored --nocapture
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//!
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//! from `scripts/rigs/ui-profile/`.
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//!
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//! Two runs today: `what_a_fling_frame_costs` (scrolling over transcript
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//! that is already folded) and `what_a_streamed_event_costs` (a reply
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//! arriving into it).
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//!
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//! `#[ignore]`d because it asserts nothing -- it prints a distribution,
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//! so `run-tests.sh` neither runs it nor can fail on it. **Release, or
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//! the numbers mean nothing**: layout is dominated by text shaping, which
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//! is an order of magnitude slower unoptimised.
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//!
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//! What it cannot answer: anything about the GPU, the present queue, or
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//! the phone's own clock. It measures the CPU half of a frame, which is
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//! where `cpu_p50` in a phone bench report comes from.
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use ai_app::ui::fixture::{PHONE_FRAME_MS, PHONE_SCALE, phone_size};
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use iris::harness::{Harness, TouchScript};
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use iris::prelude::*;
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use std::time::{Duration, Instant};
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use ui_profile::stats::summarise;
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/// Passes over the same content, alternating direction. More than two
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/// because the question the rig was built for is whether a frame's cost
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/// is first-time work (which the first pass pays and the rest do not) or
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/// work repeated every time a row comes back on screen.
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const PASSES: usize = 8;
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/// The velocity `bench_client.rs`'s fling phase uses, so a number here
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/// and a number in a phone report describe the same gesture.
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const VELOCITY: f32 = 12_000.0;
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/// A fling settles on the spline's own schedule (~2s at this velocity);
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/// this only stops a pass that somehow never settles from running away.
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const PASS_CAP_MS: u64 = 4_000;
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#[test]
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@@ -49,9 +16,8 @@ fn what_a_fling_frame_costs() {
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h.frame(0);
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h.frame(PHONE_FRAME_MS);
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// The recorded flick first, so the velocity a real finger produces is
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// in the log beside the scripted passes below.
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let flick = TouchScript::parse(include_str!("../../../../app-rust/touch/flick-120hz.touch")).unwrap();
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let flick =
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TouchScript::parse(include_str!("../../../../app-rust/touch/flick-120hz.touch")).unwrap();
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h.replay(&flick);
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println!(
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"recorded flick released at {:?}px/s; scripted passes run at {VELOCITY}px/s",
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@@ -62,8 +28,6 @@ fn what_a_fling_frame_costs() {
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let mut all_frames = Vec::new();
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let mut all_layouts = Vec::new();
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for pass in 0..PASSES {
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// Away from the newest end on the even passes and back on the
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// odd ones, the same out-and-back the bench's fling phase drives.
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let velocity = if pass % 2 == 0 { VELOCITY } else { -VELOCITY };
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let list = (opened.screen.list)(&mut h.rsc);
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list.fling(velocity);
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@@ -95,7 +59,6 @@ fn what_a_fling_frame_costs() {
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summarise("frame", &frames);
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all_frames.extend(frames);
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all_layouts.extend(layouts);
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// A moment at rest between passes, as a finger would leave.
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t += 200;
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}
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@@ -107,15 +70,6 @@ fn what_a_fling_frame_costs() {
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summarise("layout", &all_layouts);
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}
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/// The other half of a bench run, and since 2026-09-09 the expensive one:
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/// what it costs to fold one arriving event into the transcript and show
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/// it. The bench's stream phase measured `build p50 9.5ms` on Iris's
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/// phone against a fling's 0.4ms, so this is where the frame time now is.
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///
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/// Reports the fold and the widget-tree apply separately, because they
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/// are different problems with different fixes -- and reports how the
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/// cost moves as the transcript grows, which is the shape that says
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/// whether the work is per-event or per-event-times-transcript.
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#[test]
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#[ignore]
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fn what_a_streamed_event_costs() {
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@@ -134,8 +88,6 @@ fn what_a_streamed_event_costs() {
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let mut fold = Vec::new();
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let mut apply = Vec::new();
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let mut frame = Vec::new();
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// Split by whether the delta started a new markdown block, since that
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// is the delta that builds a widget rather than re-shaping one.
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let mut frame_same_block = Vec::new();
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let mut frame_new_block = Vec::new();
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let mut t = PHONE_FRAME_MS;
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@@ -171,8 +123,6 @@ fn what_a_streamed_event_costs() {
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frame_same_block.push(took);
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}
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// Where the cost sits as the transcript grows -- one line early,
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// one late, is enough to see a per-event cost from a quadratic.
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if n == 0 || n == opened.stream_tail.len() - 1 {
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println!(
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" event {n:>3} of {}: items={} fold {:?} apply {:?}",
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@@ -189,36 +139,18 @@ fn what_a_streamed_event_costs() {
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summarise("frame", &frame);
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summarise("frame/same-block", &frame_same_block);
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summarise("frame/new-block", &frame_new_block);
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// What the GPU side has to carry, which layer 1 builds but never
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// uploads and so cannot time: every primitive is re-uploaded whenever
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// the arena changes, and the buffer is recreated when its length does
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// (`ArrBuf::update`). Splitting the streamed reply into blocks trades
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// shaping cost for more widgets, so this is the number that says
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// whether that trade is free on a real GPU path.
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println!(
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" primitives on screen at the end: {}",
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h.render.active_primitive_count()
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);
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}
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/// What re-shaping a *growing* message costs, isolated from everything
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/// else a frame does -- the measurement that decides whether an
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/// incremental-text design would pay for itself (Iris, 2026-09-09:
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/// "we should definitely investigate incremental text rendering").
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///
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/// Grows one text buffer a delta at a time, the way a streamed reply
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/// grows one row, and reports what `TextBuffer::shape` costs at each
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/// length. Linear per-delta cost means the total over a reply is
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/// quadratic in its length, which is the thing an incremental shaper
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/// would remove.
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#[test]
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#[ignore]
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fn what_reshaping_a_growing_message_costs() {
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use iris::prelude::*;
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let mut h = Harness::new(phone_size(), PHONE_SCALE);
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// A reply-sized paragraph built a delta at a time. The deltas are
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// words rather than characters because that is what a model streams.
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const DELTA: &str = "the quick brown fox jumps over the lazy dog ";
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let attrs = TextAttrs::default();
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let width = Some(phone_size().x);
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@@ -250,13 +182,6 @@ fn what_reshaping_a_growing_message_costs() {
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);
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summarise("reshape", &per_delta);
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// The same measurement at the sizes real replies actually reach.
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// Measured 2026-09-09 over 7,706 top-level blocks from 3,675 real
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// assistant messages on this machine: p50 147 chars, p90 449, p99
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// 836, largest 1,580, and *nothing* above 4,000. The bench fixture's
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// streamed message is one 14,888-character block, which is 9x the
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// largest real one -- so the sizes below are what a live reshape
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// actually costs and the run above is what the benchmark measures.
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println!(" at the sizes real replies reach:");
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for chars in [147usize, 449, 836, 1580] {
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let mut sample = String::new();
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@@ -271,19 +196,11 @@ fn what_reshaping_a_growing_message_costs() {
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}
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}
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/// Where a streamed delta's cost actually is, given that `RowBlocks::
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/// apply_delta` already re-shapes only the block the delta landed in.
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/// Three candidates, all of which scale with the *whole* message rather
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/// than the delta: re-parsing the markdown to find the blocks, comparing
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/// them against the ones already drawn, and re-shaping the last block.
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#[test]
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#[ignore]
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fn where_a_streamed_deltas_cost_is() {
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use ai_app::client::markdown_blocks::{common_prefix, split_blocks};
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// A reply with real block structure -- paragraphs separated by blank
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// lines, the way a model writes -- so the last block is one paragraph
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// rather than the whole message.
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const SENTENCE: &str = "The quick brown fox jumps over the lazy dog. ";
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let mut src = String::new();
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let mut blocks = Vec::new();
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@@ -292,8 +209,6 @@ fn where_a_streamed_deltas_cost_is() {
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let mut compare = Vec::new();
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for n in 1..=400 {
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src.push_str(SENTENCE);
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// A paragraph break every eight deltas, so the trailing block
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// stays a normal size and only the message grows.
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if n % 8 == 0 {
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src.push_str("\n\n");
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}
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@@ -323,8 +238,6 @@ fn where_a_streamed_deltas_cost_is() {
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println!(" 400 deltas: {total:?} in block-splitting and comparison alone");
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}
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/// What the bench fixture's streamed tail actually is, since the cost of
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/// a delta depends entirely on how big the block it lands in gets.
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#[test]
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#[ignore]
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fn what_the_fixture_streams() {
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@@ -340,8 +253,6 @@ fn what_the_fixture_streams() {
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items = ai_app::client::transcript_fold::fold_event(&items, event);
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}
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println!("{} items -> {}", before, items.len());
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// The stress message the generator plants in the backlog: one block,
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// no blank line, just under `text_cap`'s MESSAGE_BYTES.
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let biggest = backlog
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.iter()
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.filter_map(|item| match item {
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@@ -362,8 +273,6 @@ fn what_the_fixture_streams() {
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" backlog's largest single block: {longest} chars (in a {chars}-char message of {blocks} blocks)"
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);
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}
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// The last few items are where the stream landed. Only the message
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// variants matter -- those are what a delta appends to.
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for item in items.iter().rev().take(4) {
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let (kind, text) = match item {
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TranscriptItem::AssistantMsg { text, .. } => ("AssistantMsg", text.clone()),
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