From 46ded05a72699fbd2f79c7b566a6687b8baf14ed Mon Sep 17 00:00:00 2001 From: salijagic Date: Wed, 27 May 2026 09:33:36 +0200 Subject: [PATCH] Symmetry --- Makefile | 2 +- ...ptimization_float_inlining_SoA_symmetry.md | 60 +++ .../variant_float_inlining_SoA_symmetry.cpp | 386 ++++++++++++++++++ 3 files changed, 447 insertions(+), 1 deletion(-) create mode 100644 docs/optimization_float_inlining_SoA_symmetry.md create mode 100644 variants/variant_float_inlining_SoA_symmetry.cpp diff --git a/Makefile b/Makefile index 84a3dec..653eb89 100644 --- a/Makefile +++ b/Makefile @@ -170,7 +170,7 @@ bench-suite: bench # make video : compile the code, run the simulation, and generate the video. video: run - python ./scripts/visualization.py $(CSV) $(MP4) + python3 ./scripts/visualization.py $(CSV) $(MP4) # make test : compile and run all unit tests. test: clean diff --git a/docs/optimization_float_inlining_SoA_symmetry.md b/docs/optimization_float_inlining_SoA_symmetry.md new file mode 100644 index 0000000..bd5d344 --- /dev/null +++ b/docs/optimization_float_inlining_SoA_symmetry.md @@ -0,0 +1,60 @@ +# Optimization: SoA (float version) + +- **Author**: Smail +- **Predecessor**: variant_float_inlining_SoA.cpp +- **File(s)**: variants/variant_float_inlining_SoA_symmetry.cpp +- **Status**: TBD + +## What this changes + +Implemented a LUT for calculating the distances since they are symmetric. Saves n_p/2 sqrt + +## Code (relevant snippet) + + +See `variants/variant_float_inlining_SoA.cpp`. + +## Benchmark + +Conditions: min of N runs (TBD), N_ITER=1000, -O3 -march=native -flto. +Diff is vs `variant_float_inlining`. + +### x86 + +**Machine**: TBD + +**Frequency**: TBD + +| N | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor | +| ---- | ------------ | ------------- | ------------------------- | ------------------- | +| 50 | | | | | +| 100 | | | | | +| 200 | | | | | +| 500 | | | | | + +### ARM (Apple) + +**Machine**: TBD + +**Frequency**: TBD + +| N | W(n) [Flops] | T(n) [Cycles] | Performance [Flops/Cycle] | Diff vs Predecessor | +| ---- | ------------ | ------------- | ------------------------- | ------------------- | +| 50 | | | | | +| 100 | | | | | +| 200 | | | | | +| 500 | | | | | + +## Analysis + +Layout change only, so the expectation is roughly no win on its own. The +float scalar loop already auto-vectorises in pieces with `-O3 +-march=native`, so SoA doesnt buy much over what the AoS version was +already doing. The real payoff lands in the AVX2 child. + +Verify passes against `baseline_float_n60_i500.csv` (from +`variant_float_baseline`) at the 1cm tolerance. + +## Takeaway + +Setup step for the AVX2 variant. diff --git a/variants/variant_float_inlining_SoA_symmetry.cpp b/variants/variant_float_inlining_SoA_symmetry.cpp new file mode 100644 index 0000000..3181a74 --- /dev/null +++ b/variants/variant_float_inlining_SoA_symmetry.cpp @@ -0,0 +1,386 @@ +// # Changes: SoA layout for pedestrians (file-scope arrays instead of struct fields) +// # Predecessor: variant_float_inlining.cpp + +#include "../headers/board_reduced_float.hpp" +#include "../headers/constants_float.hpp" +#include "../headers/pedestrian_reduced_float.hpp" + +#include +#include +#include +#include +#include +#include +#include +#include + +#define SEED 42 +#define BOARD_WIDTH 10.0f +#define BOARD_LENGTH 50.0f +#define WALL_EPS 1e-3f +#define BOARD_WIDTH_MINUS_WALL_EPS 9.999f + +#ifndef RANDOM_SEED +#define RANDOM_SEED 0 +#endif + +#ifndef BENCHMARK +#define BENCHMARK 0 +#endif + +using namespace std; + +// we wanna use arrays so we can implement SoA, one array per pedestrian field +vector pos_x, pos_y; +vector sb_sq; +vector sb_e_x, sb_e_y; +vector e_x, e_y; +vector curr_vel_x, curr_vel_y; +vector w_x, w_y; +vector desired_v0; +vector v_max; +vector destination_x, destination_y; +vector color; + +Pedestrian *init_pedestrians(int n_p) { +#if RANDOM_SEED + random_device rd; + mt19937 gen(rd()); +#else + mt19937 gen(SEED); +#endif + + normal_distribution velocity_gen(v0_mean, v0_std_dev); + uniform_real_distribution y_gen(0.3, BOARD_WIDTH - 0.3); + uniform_real_distribution x_gen_left(2.0, BOARD_LENGTH / 2.0); + uniform_real_distribution x_gen_right(BOARD_LENGTH / 2.0, BOARD_LENGTH - 2.0); + + // resize all arrays for this run + pos_x.resize(n_p); + pos_y.resize(n_p); + sb_sq.resize(n_p); + sb_e_x.resize(n_p); + sb_e_y.resize(n_p); + e_x.resize(n_p); + e_y.resize(n_p); + curr_vel_x.resize(n_p); + curr_vel_y.resize(n_p); + w_x.resize(n_p); + w_y.resize(n_p); + desired_v0.resize(n_p); + v_max.resize(n_p); + destination_x.resize(n_p); + destination_y.resize(n_p); + color.resize(n_p); + + int n_p_half = n_p / 2; + + for (int i = 0; i < n_p_half; i++) { + float x = x_gen_left(gen); + float y = y_gen(gen); + + float dest_x = BOARD_LENGTH + 30.0; // renamed to avoid shadowing destination_x[] + float dest_y = y; + + float init_e_x = dest_x - x; + float init_e_y = dest_y - y; + float init_e_norm = sqrt(init_e_x * init_e_x + init_e_y * init_e_y); + float init_e_unit_x = init_e_x / init_e_norm; + float init_e_unit_y = init_e_y / init_e_norm; + + float d_v0; + do { + d_v0 = velocity_gen(gen); + } while (d_v0 <= 0.1); + + float v_m = 1.3 * d_v0; + + color[i] = 0; + pos_x[i] = x; + pos_y[i] = y; + e_x[i] = init_e_unit_x; + e_y[i] = init_e_unit_y; + v_max[i] = v_m; + desired_v0[i] = d_v0; + destination_x[i] = dest_x; + destination_y[i] = dest_y; + + // Fields the Pedestrian constructor would have zero-initialized (c_v_x=c_v_y=0): + w_x[i] = 0.0f; + w_y[i] = 0.0f; + curr_vel_x[i] = 0.0f; + curr_vel_y[i] = 0.0f; + sb_sq[i] = 0.0f; + sb_e_x[i] = 0.0f; + sb_e_y[i] = 0.0f; + } + + for (int i = n_p_half; i < n_p; i++) { + float x = x_gen_right(gen); + float y = y_gen(gen); + + float dest_x = -30; + float dest_y = y; + + float init_e_x = dest_x - x; + float init_e_y = dest_y - y; + float init_e_norm = sqrt(init_e_x * init_e_x + init_e_y * init_e_y); + float init_e_unit_x = init_e_x / init_e_norm; + float init_e_unit_y = init_e_y / init_e_norm; + + float d_v0; + do { + d_v0 = velocity_gen(gen); + } while (d_v0 <= 0.1); + + float v_m = 1.3 * d_v0; + + color[i] = 1; + pos_x[i] = x; + pos_y[i] = y; + e_x[i] = init_e_unit_x; + e_y[i] = init_e_unit_y; + v_max[i] = v_m; + desired_v0[i] = d_v0; + destination_x[i] = dest_x; + destination_y[i] = dest_y; + + w_x[i] = 0.0f; + w_y[i] = 0.0f; + curr_vel_x[i] = 0.0f; + curr_vel_y[i] = 0.0f; + sb_sq[i] = 0.0f; + sb_e_x[i] = 0.0f; + sb_e_y[i] = 0.0f; + } + + return nullptr; +} + +Board init_board_without_obstacles() { return Board(BOARD_LENGTH, BOARD_WIDTH, 0, nullptr); } + +int run_simulation(Pedestrian *pedestrians, Board &board, int n_p, int n_iter, const char *dump_path) { + (void)pedestrians; +#if BENCHMARK + (void)dump_path; +#endif + +#if !BENCHMARK + const int dump_interval = 1; + + vector> samples; + + if (dump_path) { + samples.reserve(static_cast(n_iter / dump_interval + 1) * n_p); + + for (int i = 0; i < n_p; i++) { + samples.emplace_back(0, i, pos_x[i], pos_y[i], e_x[i], e_y[i], color[i]); + } + } +#endif + + // here we have real (simple) symmetry + std::vector r_ab_x_lut(n_p * n_p, 0.0); + std::vector r_ab_y_lut(n_p * n_p, 0.0); + std::vector r_ab_norm_lut(n_p * n_p, 0.0); + // use NAME[i * n_p + j] + + for (int t = 0; t < n_iter; t++) { + for (int i = 0; i < n_p; i++) { + + float desired_velocity_x = e_x[i] * desired_v0[i]; + float desired_velocity_y = e_y[i] * desired_v0[i]; + float f_alpha_dt_x = (desired_velocity_x - curr_vel_x[i]) * dt_times_tau_alpha_inv; + float f_alpha_dt_y = (desired_velocity_y - curr_vel_y[i]) * dt_times_tau_alpha_inv; + + // lut for distances + // get all distances first + for (int j = i + 1; j < n_p; j++) { + float dx = pos_x[i] - pos_x[j]; + float dy = pos_y[i] - pos_y[j]; + float norm = sqrt(dx * dx + dy * dy); + int idx = i * n_p + j; + r_ab_x_lut[idx] = dx; + r_ab_y_lut[idx] = dy; + r_ab_norm_lut[idx] = norm; + } + + + // force between pedestrians + for (int j = 0; j < n_p; j++) { + if (i == j) continue; + + // symmetry + float r_ab_x, r_ab_y, r_ab_norm; + if (i < j) { + r_ab_x = r_ab_x_lut[i * n_p + j]; + r_ab_y = r_ab_y_lut[i * n_p + j]; + r_ab_norm = r_ab_norm_lut[i * n_p + j]; + } else { + // other direction + r_ab_x = -1 * r_ab_x_lut[j * n_p + i]; + r_ab_y = -1 * r_ab_y_lut[j * n_p + i]; + r_ab_norm = r_ab_norm_lut[j * n_p + i]; + } + + + + + //float r_ab_x = pos_x[i] - pos_x[j]; + //float r_ab_y = pos_y[i] - pos_y[j]; + + //float r_ab_norm = sqrt(r_ab_x * r_ab_x + r_ab_y * r_ab_y); + r_ab_norm = r_ab_norm > EPS ? r_ab_norm : EPS; + + float r_ab2_x = r_ab_x - sb_e_x[j]; + float r_ab2_y = r_ab_y - sb_e_y[j]; + + float r_ab2_norm = sqrt(r_ab2_x * r_ab2_x + r_ab2_y * r_ab2_y); + r_ab2_norm = r_ab2_norm > EPS ? r_ab2_norm : EPS; + + float r_ab_norm_sum = r_ab_norm + r_ab2_norm; + + float two_b_sq = r_ab_norm_sum * r_ab_norm_sum - sb_sq[j]; + two_b_sq = two_b_sq > EPS_SQ ? two_b_sq : EPS_SQ; + float two_b = sqrt(two_b_sq); + float scalar_mult_common = (r_ab_norm_sum / (two_b * r_ab_norm * r_ab2_norm)) * (NEG_V0_AB_div_TWO_SIGMA * exp(two_b * NEG_TWO_SIGMA_INV)); + float scalar_mult_r_ab = scalar_mult_common * r_ab2_norm; + float scalar_mult_r_ab2 = scalar_mult_common * r_ab_norm; + + float f_alpha_beta_neg_x = r_ab_x * scalar_mult_r_ab + r_ab2_x * scalar_mult_r_ab2; + float f_alpha_beta_neg_y = r_ab_y * scalar_mult_r_ab + r_ab2_y * scalar_mult_r_ab2; + + float w_val; + + float f_norm_sq = f_alpha_beta_neg_x * f_alpha_beta_neg_x + f_alpha_beta_neg_y * f_alpha_beta_neg_y; + float rhs = f_norm_sq * cos_phi_sq; + float e_dot_f = e_x[i] * f_alpha_beta_neg_x + e_y[i] * f_alpha_beta_neg_y; + float e_dot_f_sq = e_dot_f * e_dot_f; + if (e_dot_f >= 0.0 || e_dot_f_sq <= rhs) + w_val = dt_neg; + else + w_val = c_neg_times_dt; + + f_alpha_dt_x = f_alpha_dt_x + f_alpha_beta_neg_x * w_val; + f_alpha_dt_y = f_alpha_dt_y + f_alpha_beta_neg_y * w_val; + } + + // force between pedestrian and obstacles + for (int k = 0; k < board.n_obstacles; k++) { + + float v1_x = pos_x[i] - board.obstacles[k].start_x; + float v1_y = pos_y[i] - board.obstacles[k].start_y; + float v2_x = board.obstacles[k].obstacle_v_x; + float v2_y = board.obstacles[k].obstacle_v_y; + + float projection = (v1_x * v2_x + v1_y * v2_y) * board.obstacles[k].length_sq_inv; + + if (projection < 0.0) + projection = 0.0; + else if (projection > 1.0) + projection = 1.0; + + float r_aB_x = pos_x[i] - (board.obstacles[k].start_x + board.obstacles[k].obstacle_v_x * projection); + float r_aB_y = pos_y[i] - (board.obstacles[k].start_y + board.obstacles[k].obstacle_v_y * projection); + + float r_aB_norm = sqrt(r_aB_x * r_aB_x + r_aB_y * r_aB_y); + r_aB_norm = r_aB_norm > EPS ? r_aB_norm : EPS; + + float scalar_mult = (NEG_U0_AB_div_R * exp(r_aB_norm * NEG_R_INV)) / r_aB_norm; + float f_alpha_B_neg_x = r_aB_x * scalar_mult; + float f_alpha_B_neg_y = r_aB_y * scalar_mult; + + float w_val; + + float e_dot_f = (f_alpha_B_neg_y == 0) ? 0 : (f_alpha_B_neg_y < 0 ? -e_y[i] : e_y[i]); + + if (e_dot_f >= cos_phi) + w_val = dt_neg; + else + w_val = c_neg_times_dt; + + float f_alpha_B_dt_x = f_alpha_B_neg_x * w_val; + float f_alpha_B_dt_y = f_alpha_B_neg_y * w_val; + + f_alpha_dt_x += f_alpha_B_dt_x; + f_alpha_dt_y += f_alpha_B_dt_y; + } + + w_x[i] += f_alpha_dt_x; + w_y[i] += f_alpha_dt_y; + } + + // update each pedestrian + for (int i = 0; i < n_p; i++) { + + float w_norm = sqrt(w_x[i] * w_x[i] + w_y[i] * w_y[i]); + + float w_norm2 = w_norm > EPS ? w_norm : EPS; + + float correction_factor = min(1.0f, v_max[i] / w_norm2); + + curr_vel_x[i] = w_x[i] * correction_factor; + curr_vel_y[i] = w_y[i] * correction_factor; + + pos_x[i] = pos_x[i] + curr_vel_x[i] * dt; + pos_y[i] = pos_y[i] + curr_vel_y[i] * dt; + + if (color[i] == 0 && pos_x[i] > (BOARD_LENGTH - 1.5)) { + pos_x[i] = 1.0; + destination_y[i] = pos_y[i]; + w_x[i] = desired_v0[i]; + w_y[i] = 0.0; + curr_vel_x[i] = w_x[i]; + curr_vel_y[i] = w_y[i]; + } + if (color[i] == 1 && pos_x[i] < 1.5) { + pos_x[i] = BOARD_LENGTH - 1.0; + destination_y[i] = pos_y[i]; + w_x[i] = -desired_v0[i]; + w_y[i] = 0.0; + curr_vel_x[i] = w_x[i]; + curr_vel_y[i] = w_y[i]; + } + + pos_y[i] = clamp(pos_y[i], WALL_EPS, BOARD_WIDTH_MINUS_WALL_EPS); + + float ex = destination_x[i] - pos_x[i]; + float ey = destination_y[i] - pos_y[i]; + + float e_norm = sqrt(ex * ex + ey * ey); + float e_norm2 = e_norm > EPS ? e_norm : EPS; + float e_norm_inv = 1.0 / e_norm2; + + e_x[i] = ex * e_norm_inv; + e_y[i] = ey * e_norm_inv; + + float velocity_norm_sq = curr_vel_x[i] * curr_vel_x[i] + curr_vel_y[i] * curr_vel_y[i]; + + float velocity_norm = sqrt(velocity_norm_sq); + + sb_sq[i] = velocity_norm_sq * delta_t_sq; + + sb_e_x[i] = e_x[i] * (velocity_norm * delta_t); + sb_e_y[i] = e_y[i] * (velocity_norm * delta_t); + +#if !BENCHMARK + if (dump_path && (t % dump_interval == 0)) { + samples.emplace_back(t + 1, i, pos_x[i], pos_y[i], e_x[i], e_y[i], color[i]); + } +#endif + } + } + +#if !BENCHMARK + if (dump_path) { + ofstream out(dump_path); + out << "time,id,x,y,p.e.x,p.e.y,color\n"; + + for (auto &[t, id, x, y, e_x, e_y, c] : samples) { + out << t << ',' << id << ',' << x << ',' << y << ',' << e_x << ',' << e_y << ',' << c << '\n'; + } + } +#endif + + return 0; +}