patch_size.patch

diff --git a/Eigen/src/SVD/BDCSVD.h b/Eigen/src/SVD/BDCSVD.h
index 6b85d1d5a..f7d023c7a 100644
--- a/Eigen/src/SVD/BDCSVD.h
+++ b/Eigen/src/SVD/BDCSVD.h
@@ -30,6 +30,10 @@
 // IWYU pragma: private
 #include "./InternalHeaderCheck.h"
 
+#include <tbb/parallel_reduce.h>
+
+static tbb::affinity_partitioner ap;
+
 #ifdef EIGEN_BDCSVD_DEBUG_VERBOSE
 #include <iostream>
 #endif
@@ -805,6 +809,16 @@ template <typename MatrixType, int Options>
 typename BDCSVD<MatrixType, Options>::RealScalar BDCSVD<MatrixType, Options>::secularEq(
     RealScalar mu, const ArrayRef& col0, const ArrayRef& diag, const IndicesRef& perm, const ArrayRef& diagShifted,
     RealScalar shift) {
+  return tbb::parallel_deterministic_reduce(
+      tbb::blocked_range<Index>(Index(0), perm.size()), RealScalar(1),
+      [&](const tbb::blocked_range<Index>& r, RealScalar running_total) {
+        for (auto i = r.begin(); i < r.end(); ++i) {
+          Index j = perm(i);
+          running_total += (col0(j) / (diagShifted(j) - mu)) * (col0(j) / (diag(j) + shift + mu));
+        }
+        return running_total;
+      },
+      std::plus<>());
   Index m = perm.size();
   RealScalar res = Literal(1);
   for (Index i = 0; i < m; ++i) {
@@ -1155,10 +1169,13 @@ void BDCSVD<MatrixType, Options>::computeSingVecs(const ArrayRef& zhat, const Ar
       if (m_compV) V.col(k) = VectorType::Unit(n, k);
     } else {
       U.col(k).setZero();
-      for (Index l = 0; l < m; ++l) {
-        Index i = perm(l);
-        U(i, k) = zhat(i) / (((diag(i) - shifts(k)) - mus(k))) / ((diag(i) + singVals[k]));
-      }
+      tbb::parallel_for(
+          Index(0), m,
+          [&](const Index l) {
+            Index i = perm(l);
+            U(i, k) = zhat(i) / (((diag(i) - shifts(k)) - mus(k))) / ((diag(i) + singVals[k]));
+          },
+          ap);
       U(n, k) = Literal(0);
       U.col(k).normalize();