Add trivial gemm test for multithread consistency

cpp_thread_test/gemm64.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <cblas.h>
+int main ( int argc, char* argv[] ) {
+    const long n = ((long)1 << 31) - 1;
+    std::cout << n <<std::endl;
+    float*  A = new float[n];
+    float*  B = new float[n];
+    float*  C = new float[1];
+    for(long i =0; i <n; i++){
+        A[i] = 1;
+        B[i] = 1;
+
+    }
+    cblas_sgemm(CblasRowMajor, CblasNoTrans, CblasNoTrans, 1, 1, n,  1.0, A, n, B, 1, 0.0, C, 1);
+    std::cout << *C <<std::endl;
+    delete[] A;
+    delete[] B;
+    delete[] C;
+    return 0;
+}