Files
Mujoco_WASM/test/engine/engine_util_solve_test.cc
T
Yuval Tassa 45b0153067 Refactor sparse Cholesky factorization into symbolic and numeric phases.
The new symbolic function is a generalization of the function it replaces. In this CL it takes two unused temp arrays. The actual change in behavior happens in the followup.

New benchmark test output below ("L" is 2 humanoids and 100 free objects, "XL" is 100 humanoids). Note that `symbolic` is only ever called once per Newton iteration, while `numeric` is sometimes called multiple times (when the rank-1 update fails), hence timing them separately is valuable.

```
Benchmark               Time(ns)        CPU(ns)     Iterations
--------------------------------------------------------------
BM_old_L_mean              84382          84703          19547  11.807k items/s
BM_symbolic_L_mean         16345          16381          88414  61.055k items/s
BM_numeric_L_mean          10986          10994         120000  90.999k items/s
BM_old_XL_mean           1241208        1244212           1200  803.924 items/s
BM_symbolic_XL_mean       130917         131042          12720  7.631k items/s
BM_numeric_XL_mean         77004          76767          21116  13.029k items/s
```

PiperOrigin-RevId: 846704054
Change-Id: Ib0c365724d63bf2b81606ca5353756a6496c3a26
2025-12-19 06:11:55 -08:00

1039 lines
32 KiB
C++

// Copyright 2021 DeepMind Technologies Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Tests for engine/engine_util_solve.c.
#include "src/engine/engine_util_solve.h"
#include <cstddef>
#include <iomanip>
#include <iostream>
#include <random>
#include <string>
#include <vector>
#include <gmock/gmock.h>
#include <gtest/gtest.h>
#include <mujoco/mujoco.h>
#include "src/engine/engine_util_blas.h"
#include "src/engine/engine_util_misc.h"
#include "src/engine/engine_util_sparse.h"
#include "test/fixture.h"
namespace mujoco {
namespace {
using ::testing::DoubleEq;
using ::testing::Pointwise;
using ::testing::DoubleNear;
using ::testing::ElementsAre;
using ::std::string;
using ::std::vector;
using ::std::setw;
using QCQP2Test = MujocoTest;
TEST_F(QCQP2Test, DegenerateAMatrix) {
// A 2x2 matrix with determinant zero.
const mjtNum Ain[9] { 6, -15, 2, -5 };
// Any values will do for these three inputs.
const mjtNum bin[3] { -12, 49 };
const mjtNum d[3] { 11, 31 };
const mjtNum r = 0.01;
// Make output array explicitly nonzero to simulate uninitialized memory.
mjtNum res[2] { 999, 999 };
EXPECT_EQ(mju_QCQP2(res, Ain, bin, d, r), 0);
EXPECT_EQ(res[0], 0);
EXPECT_EQ(res[1], 0);
}
using QCQP3Test = MujocoTest;
TEST_F(QCQP3Test, DegenerateAMatrix) {
// A 3x3 matrix with determinant zero.
const mjtNum Ain[9] { 1, 4, -2, -3, -7, 5, 2, -9, 0 };
// Any values will do for these three inputs.
const mjtNum bin[3] { -12, 49, 8 };
const mjtNum d[3] { 11, 31, -23 };
const mjtNum r = 0.1;
// Make output array explicitly nonzero to simulate uninitialized memory.
mjtNum res[3] { 999, 999, 999 };
EXPECT_EQ(mju_QCQP3(res, Ain, bin, d, r), 0);
EXPECT_EQ(res[0], 0);
EXPECT_EQ(res[1], 0);
EXPECT_EQ(res[2], 0);
}
// --------------------------- mju_boxQP ---------------------------------------
using BoxQPTest = MujocoTest;
// utility: compute QP objective = 0.5*x'*H*x + x'*g
mjtNum objective(const mjtNum* x, const mjtNum* H, const mjtNum* g, int n) {
return 0.5 * mju_mulVecMatVec(x, H, x, n) + mju_dot(x, g, n);
}
// utility: test if res is the minimum of a given box-QP problem
bool isQPminimum(const mjtNum* res, const mjtNum* H, const mjtNum* g, int n,
const mjtNum* lower, const mjtNum* upper) {
static const mjtNum eps = 1e-4; // epsilon used for nudging
bool is_minimum = true;
mjtNum* res_nudge = (mjtNum*) mju_malloc(sizeof(mjtNum)*n);
// get solution value
mjtNum value = objective(res, H, g, n);
mjtNum value_nudge;
// compare to nudged solution
mju_copy(res_nudge, res, n);
for (int i=0; i < n; i++) {
// nudge down
res_nudge[i] = res[i] - eps;
if (lower) {
res_nudge[i] = mju_max(lower[i], res_nudge[i]);
}
value_nudge = objective(res_nudge, H, g, n);
if (value_nudge - value < 0) {
is_minimum = false;
break;
}
// nudge up
res_nudge[i] = res[i] + eps;
if (upper) {
res_nudge[i] = mju_min(upper[i], res_nudge[i]);
}
value_nudge = objective(res_nudge, H, g, n);
if (value_nudge - value < 0) {
is_minimum = false;
break;
}
// reset
res_nudge[i] = res[i];
}
mju_free(res_nudge);
return is_minimum;
}
// utility: define QP with pseudorandom values
void randomBoxQP(int n, mjtNum* H, mjtNum* g, mjtNum* lower, mjtNum* upper,
int seed) {
// make distribution using seed
std::mt19937_64 rng;
rng.seed(seed);
std::normal_distribution<double> dist(0, 1);
// square root of H
mjtNum* sqrtH = (mjtNum*) mju_malloc(sizeof(mjtNum)*n*n);
for (int i=0; i < n; i++) {
g[i] = dist(rng);
lower[i] = 5*dist(rng);
upper[i] = 5*dist(rng);
// fix invalid bounds
if (lower[i] > upper[i]) {
mjtNum tmp = upper[i];
upper[i] = lower[i];
lower[i] = tmp;
}
// sample temp
for (int j=0; j < n; j++) {
sqrtH[n*i+j] = dist(rng);
}
}
// make SPD matrix H
mju_mulMatTMat(H, sqrtH, sqrtH, n, n, n);
mju_free(sqrtH);
}
// test mju_boxQP on a small unbounded QP
TEST_F(BoxQPTest, UnboundedQP) {
// small arrays, allocate on stack
static const int n = 2;
mjtNum H[n*n] = {
2, 0,
0, 2
};
mjtNum g[n] = {1, 3};
mjtNum res[n] = {0, 0};
mjtNum R[n*(n+7)];
int nfree = mju_boxQP(res, R, /*index=*/nullptr, H, g, n,
/*lower=*/nullptr, /*upper=*/nullptr);
// no bounds, expect Newton point
EXPECT_EQ(nfree, 2);
EXPECT_THAT(res[0], DoubleEq(-g[0]/H[0]));
EXPECT_THAT(res[1], DoubleEq(-g[1]/H[3]));
// check that solution is actual minimum
EXPECT_TRUE(isQPminimum(res, H, g, n, /*lower=*/nullptr, /*upper=*/nullptr));
// perturb solution, expected it no longer be the minimum
res[0] += 0.001;
EXPECT_FALSE(isQPminimum(res, H, g, n, /*lower=*/nullptr, /*upper=*/nullptr));
// negative-definite Hessian, no solution
H[0] = -1;
nfree = mju_boxQP(res, R, /*index=*/nullptr, H, g, n,
/*lower=*/nullptr, /*upper=*/nullptr);
EXPECT_EQ(nfree, -1);
}
// small bounded QP with asymmetric Hessian (upper triangle ignored)
TEST_F(BoxQPTest, AsymmetricUpperIgnored) {
// small arrays, allocate on stack
static const int n = 2;
mjtNum H[n*n] = {
1, -400,
0, 1
};
mjtNum g[n] = {1, 3};
mjtNum res[n] = {0, 0};
mjtNum lower[n] = {-2, -2};
mjtNum upper[n] = {0, 0};
int index[n];
mjtNum R[n*(n+7)];
// solve box-QP
int nfree = mju_boxQP(res, R, index, H, g, n, lower, upper);
EXPECT_EQ(nfree, 1);
EXPECT_THAT(res[0], DoubleEq(-g[0]/H[0]));
EXPECT_THAT(res[1], DoubleEq(lower[1]));
}
// test mju_boxQP on a single random bounded QP
TEST_F(BoxQPTest, BoundedQP) {
int n = 50; // problem size
// allocate on heap
mjtNum *H, *g, *lower, *upper; // inputs
mjtNum *res, *R; // outputs
int* index; // outputs
mju_boxQPmalloc(&res, &R, &index, &H, &g, n, &lower, &upper);
randomBoxQP(n, H, g, lower, upper, /*seed=*/1);
// initialize res
mju_zero(res, n);
// use default options
int maxiter = 100; // maximum number of iterations
mjtNum mingrad = 1E-16; // minimum squared norm of (unclamped) gradient
mjtNum backtrack = 0.5; // backtrack factor for decreasing stepsize
mjtNum minstep = 1E-22; // minimum stepsize for linesearch
mjtNum armijo = 0.1; // Armijo parameter
// logging
static const int logsz = 10000;
char log[logsz];
int nfree = mju_boxQPoption(res, R, index, H, g, n, lower, upper,
maxiter, mingrad, backtrack,
minstep, armijo, log, logsz);
// ADD_FAILURE() << log; // uncomment to print `log` to error log
// check solution
EXPECT_GT(nfree, -1);
EXPECT_TRUE(isQPminimum(res, H, g, n, lower, upper));
// verify clamping
int j = nfree > 0 ? 0 : -1;
for (int i=0; i < n; i++) {
if (j >= 0 && i == index[j]) { // free dimension
EXPECT_GT(res[i], lower[i]);
EXPECT_LT(res[i], upper[i]);
j++;
} else { // clamped dimension
EXPECT_TRUE(res[i] == lower[i] || res[i] == upper[i]);
}
}
mju_free(res);
mju_free(R);
mju_free(index);
mju_free(H);
mju_free(g);
mju_free(lower);
mju_free(upper);
}
// test mju_boxQP on a set of random bounded QPs
TEST_F(BoxQPTest, BoundedQPvariations) {
int nmax = 100;
// allocate maximum size on heap
mjtNum *H, *g, *lower, *upper; // inputs
mjtNum *res, *R; // outputs
int* index; // outputs
mju_boxQPmalloc(&res, &R, &index, &H, &g, nmax, &lower, &upper);
// logging
static const int logsz = 10000;
char log[logsz];
int seed = 1;
for (int n : {3, 30, 100}) {
int count = 0;
int factorizations = 0;
for (mjtNum scaleH : {.01, 1.0, 100.0}) {
for (mjtNum scaleg : {.01, 1.0, 100.0}) {
for (mjtNum scalebounds : {.01, 1.0, 100.0}) {
// make random box-QP
randomBoxQP(n, H, g, lower, upper, seed++);
mju_scl(H, H, scaleH, n*n);
mju_scl(g, g, scaleg, n);
mju_scl(lower, lower, scalebounds, n);
mju_scl(upper, upper, scalebounds, n);
// initialize with zeros
mju_zero(res, n);
// default algorithm options
int maxiter = 100;
mjtNum mingrad = 1E-16;
mjtNum backtrack = 0.5;
mjtNum minstep = 1E-22;
mjtNum armijo = 0.1;
// solve box-QP with logging
int nfree = mju_boxQPoption(res, R, index, H, g, n, lower, upper,
maxiter, mingrad, backtrack,
minstep, armijo, log, logsz);
// check solution
EXPECT_GT(nfree, -1) << log;
EXPECT_TRUE(isQPminimum(res, H, g, n, lower, upper))
<< "n " << n << '\n'
<< "scaleH " << scaleH << '\n'
<< "scaleg " << scaleg << '\n'
<< "scalebounds " << scalebounds << '\n';
// wrap log with string, count factorizations
string slog(log);
string factorstr = "factorizations=";
std::size_t index = slog.find(factorstr) + factorstr.length();
int num_factor = std::stoi(slog.substr(index, 3));
// never more than 6 factorizations
EXPECT_LE(num_factor, 6);
factorizations += num_factor;
count++;
}
}
}
double meanfactor = ((double)factorizations) / count;
// average of 4.5 factorizations is expected
EXPECT_LE(meanfactor, 5.0);
std::cerr << "n=" << setw(3) << n
<< ": average of " << meanfactor << " factorizations\n";
}
mju_free(res);
mju_free(R);
mju_free(index);
mju_free(H);
mju_free(g);
mju_free(lower);
mju_free(upper);
}
// ------------------------- band matrices -------------------------------------
using BandMatrixTest = MujocoTest;
// utility: random "arrowhead", banded-then-dense SPD matrix
// optional random vector and diagonal regularizer
void randomBanded(mjtNum* H, int nTotal, int nBand, int nDense, int seed,
mjtNum* vec = nullptr, mjtNum reg = 0) {
// make distribution using seed
std::mt19937_64 rng;
rng.seed(seed);
std::normal_distribution<double> dist(0, 1);
// allocate square root
mjtNum* sqrtH = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal*nTotal);
// sample
for (int i=0; i < nTotal; i++) {
if (vec) vec[i] = dist(rng);
for (int j=0; j < nTotal; j++) {
sqrtH[nTotal*i+j] = dist(rng);
}
}
// make SPD matrix H
mju_mulMatTMat(H, sqrtH, sqrtH, nTotal, nTotal, nTotal);
// set zeros
int nSparse = nTotal-nDense;
for (int i=0; i < nSparse; i++) {
int nzeros = mjMAX(0, i + 1 - nBand);
for (int j=0; j < nzeros; j++) {
H[nTotal*i + j] = 0;
H[nTotal*j + i] = 0;
}
}
// add regularizer to diagonal
for (int i=0; i < nTotal; i++) {
H[nTotal*i + i] += reg;
}
mju_free(sqrtH);
}
// test banded-vector diagonal values
TEST_F(BandMatrixTest, Diagonal) {
int seed = 1;
int nTotal = 8;
for (int nBand : {1, 3}) {
for (int nDense : {0, 2}) {
// allocate
int nB = (nTotal-nDense)*nBand + nDense*nTotal;
mjtNum* B = (mjtNum*) mju_malloc(sizeof(mjtNum)*nB);
int nH = nTotal*nTotal;
mjtNum* H = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
// make random banded SPD matrix, dense representation
randomBanded(H, nTotal, nBand, nDense, seed++);
// convert to banded representation
mju_dense2Band(B, H, nTotal, nBand, nDense);
// expect diagonals to be equal
for (int i=0; i < nTotal; i++) {
EXPECT_EQ(H[i*nTotal + i], B[mju_bandDiag(i, nTotal, nBand, nDense)]);
}
mju_free(H);
mju_free(B);
}
}
}
// test conversion of banded <-> dense
TEST_F(BandMatrixTest, Conversion) {
int seed = 1;
int nTotal = 8;
for (int nBand : {0, 1, 3}) {
for (int nDense : {0, 2}) {
// allocate
int nB = (nTotal-nDense)*nBand + nDense*nTotal;
mjtNum* B = (mjtNum*) mju_malloc(sizeof(mjtNum)*nB);
int nH = nTotal*nTotal;
mjtNum* H = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* H1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
// make random banded SPD matrix, dense
randomBanded(H, nTotal, nBand, nDense, seed++);
// convert to banded
mju_dense2Band(B, H, nTotal, nBand, nDense);
// convert back to dense
mju_band2Dense(H1, B, nTotal, nBand, nDense, /*flg_sym=*/1);
// expect exact equality
EXPECT_EQ(AsVector(H, nH), AsVector(H1, nH));
mju_free(H1);
mju_free(H);
mju_free(B);
}
}
}
// test banded-vector multiplication
TEST_F(BandMatrixTest, Multiplication) {
int seed = 1;
int nTotal = 8;
for (int nBand : {0, 1, 3}) {
for (int nDense : {0, 2}) {
// allocate
int nB = (nTotal-nDense)*nBand + nDense*nTotal;
mjtNum* B = (mjtNum*) mju_malloc(sizeof(mjtNum)*nB);
int nH = nTotal*nTotal;
mjtNum* H = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* vec = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
// make random banded SPD matrix, dense
randomBanded(H, nTotal, nBand, nDense, seed++, vec);
// multiply dense
mju_mulMatVec(res, H, vec, nTotal, nTotal);
// convert to banded, multiply
mju_dense2Band(B, H, nTotal, nBand, nDense);
mju_bandMulMatVec(res1, B, vec, nTotal, nBand, nDense,
/*nVec=*/1, /*flg_sym=*/1);
// expect numerical equality
mjtNum eps = 1e-12;
EXPECT_THAT(AsVector(res, nTotal),
Pointwise(DoubleNear(eps), AsVector(res1, nTotal)));
mju_free(res1);
mju_free(res);
mju_free(vec);
mju_free(H);
mju_free(B);
}
}
}
// test banded factorization and vector product with factor
TEST_F(BandMatrixTest, Factorization) {
int seed = 1;
int nTotal = 8;
for (int nBand : {1, 3}) {
for (int nDense : {0, 2}) {
for (mjtNum diagadd : {0.0, 1.0}) {
for (int diagmul : {0.0, 1.3}) {
// allocate
int nB = (nTotal-nDense)*nBand + nDense*nTotal;
mjtNum* B = (mjtNum*) mju_malloc(sizeof(mjtNum)*nB);
int nH = nTotal*nTotal;
mjtNum* H = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* H1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* vec = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
// make random banded matrix, dense representation
// add regularizer to ensure PD
randomBanded(H, nTotal, nBand, nDense, seed++, vec, /*reg=*/nTotal);
// convert to banded
mju_dense2Band(B, H, nTotal, nBand, nDense);
// apply diagadd and diagmul
for (int i=0; i < nTotal; i++) {
H[nTotal*i + i] += diagadd + diagmul*H[nTotal*i + i];
}
// in-place dense factorization
int rank = mju_cholFactor(H, nTotal, /*mindiag=*/0);
// expect factorization to have succeeded
EXPECT_EQ(rank, nTotal);
// banded factorization
mjtNum minDiag = mju_cholFactorBand(B, nTotal, nBand, nDense,
diagadd, diagmul);
// expect factorization to have succeeded
EXPECT_GT(minDiag, 0);
// convert back to dense, lower triangle only
mju_band2Dense(H1, B, nTotal, nBand, nDense, /*flg_sym=*/0);
// zero upper triangle of H (unused)
for (int i=0; i < nTotal-1; i++) {
mju_zero(H + nTotal*i + i + 1, nTotal - i - 1);
}
// expect numerical equality
mjtNum eps = 1e-12;
EXPECT_THAT(AsVector(H, nH),
Pointwise(DoubleNear(eps), AsVector(H1, nH)));
// multiply dense
mju_mulMatVec(res, H, vec, nTotal, nTotal);
// multiply sparse, only lower triangle
mju_bandMulMatVec(res1, B, vec, nTotal, nBand, nDense,
/*nVec=*/1, /*flg_sym=*/0);
// expect numerical equality
EXPECT_THAT(AsVector(res, nTotal),
Pointwise(DoubleNear(eps), AsVector(res1, nTotal)));
mju_free(res1);
mju_free(res);
mju_free(vec);
mju_free(H1);
mju_free(H);
mju_free(B);
}
}
}
}
}
// test banded solve
TEST_F(BandMatrixTest, Solve) {
int seed = 1;
int nTotal = 8;
for (int nBand : {1, 3}) {
for (int nDense : {0, 2}) {
// allocate
int nB = (nTotal-nDense)*nBand + nDense*nTotal;
mjtNum* B = (mjtNum*) mju_malloc(sizeof(mjtNum)*nB);
int nH = nTotal*nTotal;
mjtNum* H = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* H1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nH);
mjtNum* vec = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
mjtNum* res1 = (mjtNum*) mju_malloc(sizeof(mjtNum)*nTotal);
// make random banded matrix, dense representation
// add regularizer to ensure PD
randomBanded(H, nTotal, nBand, nDense, seed++, vec, /*reg=*/nTotal);
// convert to banded
mju_dense2Band(B, H, nTotal, nBand, nDense);
// in-place dense factorization
int rank = mju_cholFactor(H, nTotal, /*mindiag=*/0);
// expect factorization to have succeeded
EXPECT_EQ(rank, nTotal);
// banded factorization
mjtNum minDiag = mju_cholFactorBand(B, nTotal, nBand, nDense,
/*diagadd=*/0, /*diagmul=*/0);
// expect factorization to have succeeded
EXPECT_GT(minDiag, 0);
// convert back to dense, lower triangle only
mju_band2Dense(H1, B, nTotal, nBand, nDense, /*flg_sym=*/0);
// solve with dense
mju_cholSolve(res, H, vec, nTotal);
// solve with banded
mju_cholSolveBand(res1, B, vec, nTotal, nBand, nDense);
// expect numerical equality
mjtNum eps = 1e-12;
EXPECT_THAT(AsVector(res, nTotal),
Pointwise(DoubleNear(eps), AsVector(res1, nTotal)));
mju_free(res1);
mju_free(res);
mju_free(vec);
mju_free(H1);
mju_free(H);
mju_free(B);
}
}
}
using EngineUtilSolveTest = MujocoTest;
TEST_F(EngineUtilSolveTest, MjuCholFactorSymbolic) {
mjModel* model = LoadModelFromString("<mujoco/>");
mjData* d = mj_makeData(model);
// Test matrix (upper triangular, representing symmetric matrix):
// [10 1 2 3]
// [ 0 10 0 0]
// [ 0 0 10 1]
// [ 0 0 0 10]
//
// mju_cholFactorSymbolic reads entries where col >= row
int n = 4;
mjtNum H[16] = {10, 1, 2, 3, 0, 10, 0, 0, 0, 0, 10, 1, 0, 0, 0, 10};
// convert to sparse
mjtNum sparseH[16];
int H_rownnz[4], H_rowadr[4], H_colind[16];
mju_dense2sparse(sparseH, H, n, n, H_rownnz, H_rowadr, H_colind, 16);
// phase 1: counting
int L_rownnz[4], L_rowadr[4];
int LT_rownnz[4], LT_rowadr[4];
int nnz = mju_cholFactorSymbolic(nullptr, L_rownnz, L_rowadr, nullptr,
LT_rownnz, LT_rowadr, nullptr, H_rownnz,
H_rowadr, H_colind, n, d);
// verify counting phase outputs
EXPECT_EQ(nnz, 8);
// L (CSR) structure for reverse Cholesky (rows filled in reverse order)
EXPECT_THAT(AsVector(L_rownnz, 4), ElementsAre(1, 2, 2, 3));
EXPECT_THAT(AsVector(L_rowadr, 4), ElementsAre(0, 1, 3, 5));
// LT (CSC) structure: transpose of L
EXPECT_THAT(AsVector(LT_rownnz, 4), ElementsAre(4, 1, 2, 1));
EXPECT_THAT(AsVector(LT_rowadr, 4), ElementsAre(0, 4, 5, 7));
// phase 2: filling
int L_colind[8], LT_colind[8], LT_pos[8];
mju_cholFactorSymbolic(L_colind, L_rownnz, L_rowadr, LT_colind, LT_rownnz,
LT_rowadr, LT_pos, H_rownnz, H_rowadr, H_colind, n, d);
// verify L_colind
EXPECT_THAT(AsVector(L_colind, 8), ElementsAre(0, 0, 1, 0, 2, 0, 2, 3));
// Explanation (reverse Cholesky builds from bottom to top):
// Row 0 (1 entry): diagonal 0
// Row 1 (2 entries): col 0, then diagonal 1
// Row 2 (2 entries): col 0, then diagonal 2
// Row 3 (3 entries): col 0, col 2, then diagonal 3
// verify LT_colind: transpose of L
EXPECT_THAT(AsVector(LT_colind, 8), ElementsAre(0, 1, 2, 3, 1, 2, 3, 3));
// Explanation:
// Column 0 (4 entries): rows 0, 1, 2, 3 (all have L[row, 0] != 0)
// Column 1 (1 entry): row 1
// Column 2 (2 entries): rows 2, 3
// Column 3 (1 entry): row 3
// verify LT_pos: for each entry in LT, should point to correct position in L
for (int c = 0; c < n; c++) {
int adr = LT_rowadr[c];
for (int k = 0; k < LT_rownnz[c]; k++) {
int L_idx = LT_pos[adr + k];
EXPECT_EQ(L_colind[L_idx], c)
<< "LT_pos mismatch at column " << c << ", entry " << k;
}
}
mj_deleteData(d);
mj_deleteModel(model);
}
// Test for mju_cholUpdate: rank-one Cholesky update L*L' +/- x*x'
// Verifies that after applying the update, reconstructing H = L*L' produces
// the expected result H_original +/- x*x'.
TEST_F(EngineUtilSolveTest, MjuCholUpdate) {
std::mt19937_64 rng;
rng.seed(42);
std::normal_distribution<double> dist(0, 1);
for (int n : {4, 6, 8}) {
vector<mjtNum> H(n * n);
vector<mjtNum> H_expected(n * n);
vector<mjtNum> L_dense(n * n);
vector<mjtNum> sqrtH(n * n);
vector<mjtNum> x(n);
vector<mjtNum> x_copy(n);
vector<mjtNum> H_reconstructed(n * n);
for (int flg_plus : {0, 1}) {
// generate random lower-triangular matrix for sqrtH
mju_zero(sqrtH.data(), n * n);
for (int i = 0; i < n; i++) {
for (int j = 0; j <= i; j++) {
sqrtH[n * i + j] = dist(rng);
}
sqrtH[n * i + i] = mju_abs(sqrtH[n * i + i]) + n;
}
// create SPD matrix H = sqrtH * sqrtH' (forward-order Cholesky: L*L')
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
mjtNum sum = 0;
for (int k = 0; k <= mju_min(i, j); k++) {
sum += sqrtH[n * i + k] * sqrtH[n * j + k];
}
H[n * i + j] = sum;
}
}
// generate random update vector x
for (int i = 0; i < n; i++) {
x[i] = dist(rng) * 0.5;
}
// compute expected result: H_expected = H +/- x*x'
mju_copy(H_expected.data(), H.data(), n * n);
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (flg_plus) {
H_expected[i * n + j] += x[i] * x[j];
} else {
H_expected[i * n + j] -= x[i] * x[j];
}
}
}
// test using dense Cholesky (forward-order: L*L')
mju_copy(L_dense.data(), H.data(), n * n);
// dense factorization
int rank_factor = mju_cholFactor(L_dense.data(), n, 0);
EXPECT_EQ(rank_factor, n) << "Initial factorization failed";
// make copy of x for update (it's modified in-place)
mju_copy(x_copy.data(), x.data(), n);
// apply dense rank-one update
int rank_update =
mju_cholUpdate(L_dense.data(), x_copy.data(), n, flg_plus);
EXPECT_EQ(rank_update, n)
<< "Dense update rank loss for n=" << n << ", flg_plus=" << flg_plus;
// zero out upper triangle (Cholesky only uses lower triangle)
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
L_dense[i * n + j] = 0;
}
}
// reconstruct H from L*L' and compare to expected
mju_mulMatMatT(H_reconstructed.data(), L_dense.data(), L_dense.data(), n,
n, n);
// compare
mjtNum eps = 1e-8;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
EXPECT_NEAR(H_reconstructed[i * n + j], H_expected[i * n + j], eps)
<< "Dense mismatch at (" << i << "," << j << ") for n=" << n
<< ", flg_plus=" << flg_plus;
}
}
}
}
}
// Test for mju_cholUpdateSparse: sparse rank-one Cholesky update L'*L +/- x*x'
// Uses sparse reverse Cholesky factorization and sparse rank-one update.
TEST_F(EngineUtilSolveTest, MjuCholUpdateSparse) {
mjModel* model = LoadModelFromString("<mujoco/>");
mjData* d = mj_makeData(model);
std::mt19937_64 rng;
rng.seed(123);
std::normal_distribution<double> dist(0, 1);
for (int n : {4, 6, 8}) {
int max_nnz = n * (n + 1) / 2;
vector<mjtNum> H(n * n);
vector<mjtNum> H_lower(n * n);
vector<mjtNum> H_expected(n * n);
vector<mjtNum> sqrtH(n * n);
vector<mjtNum> L_sparse(max_nnz);
vector<int> rownnz(n);
vector<int> rowadr(n);
vector<int> colind(max_nnz);
vector<mjtNum> x(n);
vector<mjtNum> x_sparse(n);
vector<int> x_ind(n);
vector<mjtNum> L_sparse_dense(n * n);
vector<mjtNum> H_sparse_reconstructed(n * n);
for (int flg_plus : {0, 1}) {
// generate random lower-triangular matrix for sqrtH
mju_zero(sqrtH.data(), n * n);
for (int i = 0; i < n; i++) {
for (int j = 0; j <= i; j++) {
sqrtH[n * i + j] = dist(rng);
}
sqrtH[n * i + i] = mju_abs(sqrtH[n * i + i]) + n;
}
// create SPD matrix H = sqrtH * sqrtH' (forward-order: L*L')
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
mjtNum sum = 0;
for (int k = 0; k <= mju_min(i, j); k++) {
sum += sqrtH[n * i + k] * sqrtH[n * j + k];
}
H[n * i + j] = sum;
}
}
// generate random update vector x
for (int i = 0; i < n; i++) {
x[i] = dist(rng) * 0.5;
}
// compute expected result: H_expected = H +/- x*x'
mju_copy(H_expected.data(), H.data(), n * n);
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
if (flg_plus) {
H_expected[i * n + j] += x[i] * x[j];
} else {
H_expected[i * n + j] -= x[i] * x[j];
}
}
}
// copy H to H_lower and zero upper triangle (sparse expects lower only)
mju_copy(H_lower.data(), H.data(), n * n);
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
H_lower[i * n + j] = 0;
}
}
// convert lower-triangular H to sparse format
mju_dense2sparse(L_sparse.data(), H_lower.data(), n, n, rownnz.data(),
rowadr.data(), colind.data(), max_nnz);
// prepare sparse update vector (all elements, fully dense)
int x_nnz = n;
mju_copy(x_sparse.data(), x.data(), n);
for (int i = 0; i < n; i++) {
x_ind[i] = i;
}
// sparse Cholesky factorization (reverse-order: L'*L)
mju_cholFactorSparse(L_sparse.data(), n, 0, rownnz.data(), rowadr.data(),
colind.data(), d);
// apply sparse rank-one update
int rank_sparse = mju_cholUpdateSparse(
L_sparse.data(), x_sparse.data(), n, flg_plus, rownnz.data(),
rowadr.data(), colind.data(), x_nnz, x_ind.data(), d);
EXPECT_EQ(rank_sparse, n)
<< "Sparse update rank loss for n=" << n << ", flg_plus=" << flg_plus;
// reconstruct H from L'*L and compare to expected
mju_sparse2dense(L_sparse_dense.data(), L_sparse.data(), n, n,
rownnz.data(), rowadr.data(), colind.data());
mju_mulMatTMat(H_sparse_reconstructed.data(), L_sparse_dense.data(),
L_sparse_dense.data(), n, n, n);
// compare
mjtNum eps = 1e-8;
for (int i = 0; i < n; i++) {
for (int j = 0; j < n; j++) {
EXPECT_NEAR(H_sparse_reconstructed[i * n + j], H_expected[i * n + j],
eps)
<< "Sparse mismatch at (" << i << "," << j << ") for n=" << n
<< ", flg_plus=" << flg_plus;
}
}
}
}
mj_deleteData(d);
mj_deleteModel(model);
}
// Test that mju_cholFactorSymbolic + mju_cholFactorNumeric produces identical
// results to the reference implementation mju_cholFactorSparse
TEST_F(EngineUtilSolveTest, CholFactorSymbolicNumeric) {
mjModel* model = LoadModelFromString("<mujoco/>");
mjData* d = mj_makeData(model);
// test matrix with fill-in: upper triangle structure
int n = 4;
mjtNum H[16] = {10, 1, 2, 3, 1, 10, 0, 0, 2, 0, 10, 1, 3, 0, 1, 10};
// convert to sparse (lower triangle only)
mjtNum sparseH[16];
int H_rownnz[4], H_rowadr[4], H_colind[16];
mju_dense2sparse(sparseH, H, n, n, H_rownnz, H_rowadr, H_colind, 16);
// transpose for upper triangle (needed by cholFactorSymbolic)
int HT_rownnz[4], HT_rowadr[4], HT_colind[16];
mju_transposeSparse(nullptr, nullptr, n, n, HT_rownnz, HT_rowadr, HT_colind,
nullptr, H_rownnz, H_rowadr, H_colind);
// count fill-in (also computes LT structure)
int L_rownnz[4], L_rowadr[4];
int LT_rownnz[4], LT_rowadr[4];
int nnz = mju_cholFactorSymbolic(nullptr, L_rownnz, L_rowadr, nullptr,
LT_rownnz, LT_rowadr, nullptr, HT_rownnz,
HT_rowadr, HT_colind, n, d);
// filling phase: compute L_colind, LT_colind, and LT_pos
int L_colind[16], LT_colind[16], LT_pos[16];
mju_cholFactorSymbolic(L_colind, L_rownnz, L_rowadr, LT_colind, LT_rownnz,
LT_rowadr, LT_pos, HT_rownnz, HT_rowadr, HT_colind, n,
d);
// verify LT structure matches what we'd get from a separate transpose
int LT_rownnz_ref[4], LT_rowadr_ref[4], LT_colind_ref[16];
mju_transposeSparse(nullptr, nullptr, n, n, LT_rownnz_ref, LT_rowadr_ref,
LT_colind_ref, nullptr, L_rownnz, L_rowadr, L_colind);
// LT structure should match
EXPECT_THAT(AsVector(LT_rownnz, 4),
ElementsAre(LT_rownnz_ref[0], LT_rownnz_ref[1], LT_rownnz_ref[2],
LT_rownnz_ref[3]));
EXPECT_THAT(AsVector(LT_rowadr, 4),
ElementsAre(LT_rowadr_ref[0], LT_rowadr_ref[1], LT_rowadr_ref[2],
LT_rowadr_ref[3]));
// verify LT_colind and LT_pos match
for (int r = 0; r < n; r++) {
int adr = LT_rowadr[r];
for (int k = 0; k < LT_rownnz[r]; k++) {
int L_idx = LT_pos[adr + k]; // index in L array
// verify L_colind at this position is indeed r
EXPECT_EQ(L_colind[L_idx], r)
<< "LT_pos mismatch at LT[" << r << ", " << k << "]";
}
}
// numeric factorization using new function
mjtNum L_new[16];
int rank_new = mju_cholFactorNumeric(
L_new, n, 1e-10, L_rownnz, L_rowadr, L_colind, LT_rownnz, LT_rowadr,
LT_colind, LT_pos, sparseH, H_rownnz, H_rowadr, H_colind, d);
// reference implementation: copy sparse H into L_ref, then factor in-place
mjtNum L_ref[16];
int L_ref_rownnz[4], L_ref_colind[16];
for (int r = 0; r < n; r++) {
int nnz_r = H_rownnz[r];
// count lower triangle elements for this row
int lower_nnz = 0;
for (int i = 0; i < nnz_r; i++) {
if (H_colind[H_rowadr[r] + i] <= r) {
L_ref[L_rowadr[r] + lower_nnz] = sparseH[H_rowadr[r] + i];
L_ref_colind[L_rowadr[r] + lower_nnz] = H_colind[H_rowadr[r] + i];
lower_nnz++;
}
}
L_ref_rownnz[r] = lower_nnz;
}
int rank_ref = mju_cholFactorSparse(L_ref, n, 1e-10, L_ref_rownnz, L_rowadr,
L_ref_colind, d);
// compare results
EXPECT_EQ(rank_new, rank_ref);
EXPECT_EQ(rank_new, n);
// compare L values
mjtNum eps = 1e-10;
for (int i = 0; i < nnz; i++) {
EXPECT_NEAR(L_new[i], L_ref[i], eps) << "mismatch at index " << i;
}
mj_deleteData(d);
mj_deleteModel(model);
}
} // namespace
} // namespace mujoco