Replace std::hash with abs::Hash from the abseil library to make hash…

…ing reproducible on different systems

conanfile.py

@@ -69,6 +69,7 @@ def requirements(self):
         self.requires("spdlog/1.11.0", transitive_headers=True, transitive_libs=True)
         # nlohmann_json: public headers include json.hpp and json_fwd.hpp
         self.requires("nlohmann_json/3.11.2", transitive_headers=True)
+        self.requires("20230125.3")
         if self.options.with_python:
             self.requires("pybind11/2.10.1")
         if self.options.with_testing:

src/PROPOSAL/CMakeLists.txt

@@ -18,6 +18,7 @@ target_include_directories(PROPOSAL PUBLIC
 find_package(CubicInterpolation REQUIRED)
 find_package(spdlog REQUIRED)
 find_package(nlohmann_json REQUIRED)
+find_package(absl REQUIRED)
 
 add_subdirectory(PROPOSAL)
 add_subdirectory(detail)
@@ -26,6 +27,7 @@ target_link_libraries(PROPOSAL
     CubicInterpolation::CubicInterpolation
     spdlog::spdlog
     nlohmann_json::nlohmann_json
+    absl::hash
     )
 
 install(TARGETS PROPOSAL EXPORT PROPOSALTargets

src/PROPOSAL/PROPOSAL/methods.h

@@ -34,6 +34,7 @@
 #include <memory>
 #include <vector>
 #include <sys/stat.h>
+#include "absl/hash/hash.h"
 // use unistd.h for access on POSIX os, use io.h for windows systems
 // todo: use filesystem instead when switching to c++17
 #ifdef _WIN32
@@ -77,7 +78,7 @@ inline void hash_combine(std::size_t& seed) { (void)seed; }
 template <typename T, typename... Rest>
 inline void hash_combine(std::size_t& seed, const T& v, Rest... rest)
 {
-    std::hash<T> hasher;
+    absl::Hash<T> hasher;
     seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
     hash_combine(seed, rest...);
 }