Fix non-determinism in global placement caused by different FFT output values

src/CMakeLists.txt

@@ -192,6 +192,9 @@ add_compile_options(
   -Wno-sign-compare
   -Wp,-D_GLIBCXX_ASSERTIONS
   $<$<CXX_COMPILER_ID:Clang>:-Wno-gnu-zero-variadic-macro-arguments>
+  # Needed for floating point stability in FFT (fft_test will check this).
+  # See also https://kristerw.github.io/2021/11/09/fp-contract/
+  -ffp-contract=off
   # Apple clang 14.0.0 deprecates sprintf, which generates 900 warnings.
   $<$<CXX_COMPILER_ID:AppleClang>:-Wno-deprecated-declarations>
   $<$<BOOL:${ASAN}>:-fsanitize=address>

src/gpl/CMakeLists.txt

@@ -149,4 +149,4 @@ if (Python3_FOUND AND BUILD_PYTHON)
 
 endif()
 
-add_subdirectory(test)
+add_subdirectory(test)

src/gpl/test/CMakeLists.txt

@@ -1,3 +1,5 @@
+include("openroad")
+
 find_program (BASH_PROGRAM bash REQUIRED)
 
 function(gpl_test test_name)
@@ -41,3 +43,31 @@ clust02
 foreach(TEST_NAME IN LISTS TEST_NAMES)
   gpl_test(${TEST_NAME})
 endforeach()
+
+add_executable(fft_test fft_test.cc)
+
+target_include_directories(fft_test
+  PUBLIC
+  ${PROJECT_SOURCE_DIR}
+)
+
+target_link_libraries(fft_test
+  gtest
+  gtest_main
+  spdlog::spdlog
+)
+
+gtest_discover_tests(fft_test
+    WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
+)
+
+target_sources(fft_test
+  PRIVATE
+  fft_test.cc
+  ../src/fft.cpp
+  ../src/fftsg.cpp
+  ../src/fftsg2d.cpp
+)
+
+
+add_dependencies(build_and_test fft_test)

src/gpl/test/fft_test.cc

@@ -0,0 +1,149 @@
+#include "src/gpl/src/fft.h"
+
+#include <iostream>
+#include <memory>
+#include <sstream>
+
+#include "gtest/gtest.h"
+#include "spdlog/fmt/fmt.h"
+
+namespace {
+
+const int X_MAX = 4;
+const int Y_MAX = 4;
+
+float input_data[X_MAX * Y_MAX] = {
+    0.0,     // 0, 0
+    1.0,     // 1, 0
+    2.0,     // 2, 0
+    3.0,     // 3, 0
+    512.0,   // 0, 1
+    513.0,   // 1, 1
+    514.0,   // 2, 1
+    515.0,   // 3, 1
+    1024.0,  // 0, 2
+    1025.0,  // 1, 2
+    1026.0,  // 2, 2
+    1027.0,  // 3, 2
+    1536.0,  // 0, 3
+    1537.0,  // 1, 3
+    1538.0,  // 2, 3
+    1539.0,  // 3, 3
+};
+
+// clang-format off
+float output_data_eForce_first[X_MAX * Y_MAX] = {
+       -0.81241744756698608398, // 0, 0
+       -1.83704113960266113281, // 1, 0
+       -1.83704113960266113281, // 2, 0
+       -0.81241744756698608398, // 3, 0
+       -0.81241744756698608398, // 0, 1
+       -1.83704113960266113281, // 1, 1
+       -1.83704113960266113281, // 2, 1
+       -0.81241744756698608398, // 3, 1
+       -0.81241744756698608398, // 0, 2
+       -1.83704113960266113281, // 1, 2
+       -1.83704113960266113281, // 2, 2
+       -0.81241744756698608398, // 3, 2
+       -0.81241744756698608398, // 0, 3
+       -1.83704113960266113281, // 1, 3
+       -1.83704113960266113281, // 2, 3
+       -0.81241744756698608398, // 3, 3
+};
+
+float output_data_eForce_second[X_MAX * Y_MAX] = {
+     -415.95773315429687500000, // 0, 0
+     -415.95773315429687500000, // 1, 0
+     -415.95773315429687500000, // 2, 0
+     -415.95773315429687500000, // 3, 0
+     -940.56506347656250000000, // 0, 1
+     -940.56506347656250000000, // 1, 1
+     -940.56506347656250000000, // 2, 1
+     -940.56506347656250000000, // 3, 1
+     -940.56506347656250000000, // 0, 2
+     -940.56506347656250000000, // 1, 2
+     -940.56506347656250000000, // 2, 2
+     -940.56506347656250000000, // 3, 2
+     -415.95773315429687500000, // 0, 3
+     -415.95773315429687500000, // 1, 3
+     -415.95773315429687500000, // 2, 3
+     -415.95773315429687500000, // 3, 3
+};
+
+float output_data_electroPhi[X_MAX * Y_MAX] = {
+    -1215.75781250000000000000, // 0, 0
+    -1214.34777832031250000000, // 1, 0
+    -1212.42810058593750000000, // 2, 0
+    -1211.01806640625000000000, // 3, 0
+     -493.78292846679687500000, // 0, 1
+     -492.37280273437500000000, // 1, 1
+     -490.45324707031250000000, // 2, 1
+     -489.04312133789062500000, // 3, 1
+      489.04312133789062500000, // 0, 2
+      490.45324707031250000000, // 1, 2
+      492.37280273437500000000, // 2, 2
+      493.78292846679687500000, // 3, 2
+     1211.01806640625000000000, // 0, 3
+     1212.42810058593750000000, // 1, 3
+     1214.34777832031250000000, // 2, 3
+     1215.75781250000000000000, // 3, 3
+};
+// clang-format on
+
+void print_tables(std::unique_ptr<gpl::FFT>& fft)
+{
+  std::stringstream out_ef_1st;
+  std::stringstream out_ef_2nd;
+  std::stringstream out_el_phi;
+
+  out_ef_1st << "float output_data_eForce_first[X_MAX * Y_MAX] = {\n";
+  out_ef_2nd << "float output_data_eForce_second[X_MAX * Y_MAX] = {\n";
+  out_el_phi << "float output_data_electroPhi[X_MAX * Y_MAX] = {\n";
+  for (int y = 0; y < Y_MAX; y++) {
+    for (int x = 0; x < X_MAX; x++) {
+      auto eForce = fft->getElectroForce(x, y);
+      auto electroPhi = fft->getElectroPhi(x, y);
+      out_ef_1st << fmt::format(
+          "    {: 26.20f}, // {:d}, {:d}\n", eForce.first, x, y);
+      out_ef_2nd << fmt::format(
+          "    {: 26.20f}, // {:d}, {:d}\n", eForce.second, x, y);
+      out_el_phi << fmt::format(
+          "    {: 26.20f}, // {:d}, {:d}\n", electroPhi, x, y);
+    }
+  }
+  out_ef_1st << "};\n\n";
+  out_ef_2nd << "};\n\n";
+  out_el_phi << "};\n\n";
+
+  std::cout << out_ef_1st.str();
+  std::cout << out_ef_2nd.str();
+  std::cout << out_el_phi.str();
+}
+
+TEST(FloatFFTTest, Basic)
+{
+  std::unique_ptr<gpl::FFT> fft(new gpl::FFT(X_MAX, Y_MAX, X_MAX, Y_MAX));
+
+  for (int y = 0; y < Y_MAX; y++) {
+    for (int x = 0; x < X_MAX; x++) {
+      fft->updateDensity(x, y, input_data[x + y * Y_MAX]);
+    }
+  }
+
+  fft->doFFT();
+
+  print_tables(fft);
+
+  for (int y = 0; y < Y_MAX; y++) {
+    for (int x = 0; x < X_MAX; x++) {
+      auto eForce = fft->getElectroForce(x, y);
+      auto electroPhi = fft->getElectroPhi(x, y);
+
+      EXPECT_EQ(eForce.first, output_data_eForce_first[x + y * Y_MAX]);
+      EXPECT_EQ(eForce.second, output_data_eForce_second[x + y * Y_MAX]);
+      EXPECT_EQ(electroPhi, output_data_electroPhi[x + y * Y_MAX]);
+    }
+  }
+}
+
+}  // namespace