revert to threadpool (clang 10 compatibility issue)

test/readreftable-test.cpp

@@ -7,7 +7,7 @@
 #include <vector>
 #include <algorithm>
 #include <numeric>
-#include <execution>
+// #include <execution>
 
 #define H5_USE_EIGEN
 #include <highfive/H5Easy.hpp>
@@ -21,7 +21,7 @@
 #include "readreftable.hpp"
 #include "statobsTest.hpp"
 #include "readstatobs.hpp"
-// #include "threadpool.hpp"
+#include "threadpool.hpp"
 
 #include "H5Cpp.h"
 
@@ -90,7 +90,8 @@ void test_random_lines(HighFive::File &file, const string &dataname, const Matri
  std::shuffle(std::begin(indices), std::end(indices), g);
 
  auto loopvec = views::ints((size_t)0u,nloop) | to<std::vector>();
- std::for_each(std::execution::par,loopvec.begin(),loopvec.end(), [&](size_t j) {
+ // std::for_each(std::execution::par,loopvec.begin(),loopvec.end(), [&](size_t j) {
+ ThreadPool::ParallelFor((size_t)0u, nloop, [&](size_t j) {
  auto i = indices[j];
  auto row = p.row(i);
  const auto &expected = Catch::Matchers::ApproxRng<std::vector<double>>(row);