Fix warnings about repeated deinitions of macros.

Eigen/src/ThreadPool/CoreThreadPoolDevice.h

diff --git a/Eigen/src/ThreadPool/CoreThreadPoolDevice.h b/Eigen/src/ThreadPool/CoreThreadPoolDevice.h
index ad786fe..acf1d62 100644
--- a/Eigen/src/ThreadPool/CoreThreadPoolDevice.h
+++ b/Eigen/src/ThreadPool/CoreThreadPoolDevice.h
@@ -15,24 +15,24 @@
 // CoreThreadPoolDevice provides an easy-to-understand Device for parallelizing Eigen Core expressions with
 // Threadpool. Expressions are recursively split evenly until the evaluation cost is less than the threshold for
 // delegating the task to a thread.
-
-//                a
-//               / \
-//              /   \
-//             /     \
-//            /       \
-//           /         \
-//          /           \
-//         /             \
-//        a               e
-//       / \             / \
-//      /   \           /   \
-//     /     \         /     \
-//    a       c       e       g
-//   / \     / \     / \     / \
-//  /   \   /   \   /   \   /   \
-// a     b c     d e     f g     h
-
+/*
+                 a
+                / \
+               /   \
+              /     \
+             /       \
+            /         \
+           /           \
+          /             \
+         a               e
+        / \             / \
+       /   \           /   \
+      /     \         /     \
+     a       c       e       g
+    / \     / \     / \     / \
+   /   \   /   \   /   \   /   \
+  a     b c     d e     f g     h
+*/
 // Each task descends the binary tree to the left, delegates the right task to a new thread, and continues to the
 // left. This ensures that work is evenly distributed to the thread pool as quickly as possible and minimizes the number
 // of tasks created during the evaluation. Consider an expression that is divided into 8 chunks. The

test/assignment_threaded.cpp

diff --git a/test/assignment_threaded.cpp b/test/assignment_threaded.cpp
index 0ba8c21..7505a10 100644
--- a/test/assignment_threaded.cpp
+++ b/test/assignment_threaded.cpp
@@ -7,13 +7,10 @@
 // Public License v. 2.0. If a copy of the MPL was not distributed
 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-#if defined(EIGEN_USE_THREADS)
-#undef EIGEN_USE_THREADS
-#endif
-
-#define EIGEN_USE_THREADS
+#define EIGEN_USE_THREADS 1
 
 #include "main.h"
+#include <Eigen/ThreadPool>
 
 namespace Eigen {
 namespace internal {

test/main.h

diff --git a/test/main.h b/test/main.h
index ca485ba..e86c584 100644
--- a/test/main.h
+++ b/test/main.h
@@ -52,9 +52,6 @@
 #if __cplusplus >= 201103L || (defined(_MSVC_LANG) && _MSVC_LANG >= 201103L)
 #include <random>
 #include <chrono>
-#ifdef EIGEN_USE_THREADS
-#include <Eigen/ThreadPool>
-#endif
 #endif
 #if __cplusplus > 201703L
 // libstdc++ 9's <memory> indirectly uses max() via <bit>.
@@ -219,11 +216,7 @@
 }  // namespace Eigen
 
 #define TRACK std::cerr << __FILE__ << " " << __LINE__ << std::endl
-// #define TRACK while()
 
-#ifdef EIGEN_DEFAULT_IO_FORMAT
-#undef EIGEN_DEFAULT_IO_FORMAT
-#endif
 #define EIGEN_DEFAULT_IO_FORMAT IOFormat(4, 0, "  ", "\n", "", "", "", "")
 
 #if (defined(_CPPUNWIND) || defined(__EXCEPTIONS)) && !defined(__CUDA_ARCH__) && !defined(__HIP_DEVICE_COMPILE__) && \