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Further speedup to CSR back-substitution using dof_simplenum.

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PiperOrigin-RevId: 711440268
Change-Id: I81cd9a6a8b8ec78d08cfbc34f60a9216ea753833
This commit is contained in:
Yuval Tassa
2025-01-02 09:03:54 -08:00
committed by Copybara-Service
parent 69c9ac074a
commit 4510c6d290
5 changed files with 85 additions and 15 deletions
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src/engine/engine_core_smooth.c
+17 -10
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@@ -1575,15 +1575,19 @@ void mj_solveLD(const mjModel* m, mjtNum* restrict x, int n,
// in-place sparse backsubstitution: x = inv(L'*D*L)*x
// like mj_solveLD, but using the CSR representation of L
void mj_solveLDs(mjtNum* restrict x, const mjtNum* qLDs, const mjtNum* qLDiagInv, int nv,
const int* rownnz, const int* rowadr, const int* diag, const int* colind) {
const int* rownnz, const int* rowadr, const int* diagind, const int* diagnum,
const int* colind) {
// x <- L^-T x
for (int i=nv-2; i >= 0; i--) {
int d1 = diag[i] + 1;
int nnz = rownnz[i] - d1;
if (nnz > 0) {
int adr = rowadr[i] + d1;
x[i] -= mju_dotSparse(qLDs+adr, x, nnz, colind+adr, /*flg_unc1=*/0);
// skip diagonal (simple) rows
if (diagnum[i]) {
continue;
}
int d1 = diagind[i] + 1;
int nnz = rownnz[i] - d1;
int adr = rowadr[i] + d1;
x[i] -= mju_dotSparse(qLDs+adr, x, nnz, colind+adr, /*flg_unc1=*/0);
}
// x(i) /= D(i,i)
@@ -1593,11 +1597,14 @@ void mj_solveLDs(mjtNum* restrict x, const mjtNum* qLDs, const mjtNum* qLDiagInv
// x <- L^-1 x
for (int i=1; i < nv; i++) {
int d = diag[i];
if (d > 0) {
int adr = rowadr[i];
x[i] -= mju_dotSparse(qLDs+adr, x, d, colind+adr, /*flg_unc1=*/0);
// skip diagonal (simple) rows
if (diagnum[i]) {
i += diagnum[i] - 1; // when iterating forward we can skip ahead
continue;
}
int adr = rowadr[i];
x[i] -= mju_dotSparse(qLDs+adr, x, diagind[i], colind+adr, /*flg_unc1=*/0);
}
}