replace random function to make CI reproducible

.github/workflows/cpp.yml

@@ -107,4 +107,4 @@ jobs:
     - name: Run C++ field Tests
       working-directory: ./icicle/build/tests
       if: needs.check-changed-files.outputs.cpp == 'true'
-      run: ctest
+      run: ctest --output-on-failure

icicle/include/icicle/fields/field.h

@@ -24,6 +24,7 @@
 #endif // __CUDACC__
 
 #include "icicle/errors.h"
+#include "icicle/utils/rand_gen.hpp"
 #include "host_math.h"
 #include "storage.h"
 
@@ -689,14 +690,14 @@ class Field
     return rv;
   }
 
+  // NOTE this function is used for test and examples - it assumed it is executed on a single-thread (no two threads
+  // accessing rand_generator at the same time)
   static HOST_INLINE Field rand_host()
   {
-    std::random_device rd;
-    std::mt19937_64 generator(rd());
     std::uniform_int_distribution<unsigned> distribution;
     Field value{};
     for (unsigned i = 0; i < TLC; i++)
-      value.limbs_storage.limbs[i] = distribution(generator);
+      value.limbs_storage.limbs[i] = distribution(rand_generator);
     while (lt(Field{get_modulus()}, value))
       value = value - Field{get_modulus()};
     return value;

icicle/include/icicle/utils/rand_gen.hpp

@@ -0,0 +1,5 @@
+#pragma once
+#include <random>
+
+inline std::mt19937 rand_generator = std::mt19937{std::random_device{}()};
+static void seed_rand_generator(unsigned seed) { rand_generator.seed(seed); }

icicle/tests/test_base.h

@@ -1,8 +1,11 @@
 #pragma once
+#include <time.h>
+#include <random>
 
 #include <gtest/gtest.h>
 #include "icicle/runtime.h"
 #include "icicle/utils/log.h"
+#include "icicle/utils/rand_gen.hpp"
 
 using FpMiliseconds = std::chrono::duration<float, std::chrono::milliseconds::period>;
 #define START_TIMER(timer) auto timer##_start = std::chrono::high_resolution_clock::now();
@@ -25,6 +28,10 @@ class IcicleTestBase : public ::testing::Test
   // SetUpTestSuite/TearDownTestSuite are called once for the entire test suite
   static void SetUpTestSuite()
   {
+    unsigned seed = time(NULL);
+    srand(seed);
+    ICICLE_LOG_INFO << "Seed for tests is: " << seed;
+    seed_rand_generator(seed);
 #ifdef BACKEND_BUILD_DIR
     setenv("ICICLE_BACKEND_INSTALL_DIR", BACKEND_BUILD_DIR, 0 /*=replace*/);
 #endif