[What] Use half_float::half instead of ck::half_t for host reduction

[Why]  std::numeric_limits<_Float16>::lowest() will return zero

example/19_gemm_softmax/gemm_softmax_xdl_fp16.cpp

@@ -41,6 +41,10 @@ using BDataType   = F16;
 using CDataType   = F16;
 using AccDataType = F32;
 
+// CAUSION - host reduce_max will call numeric_limits<ck::half_t>::lowest()
+// However, numeric_limits<ck::half_t>::lowest() will return zero. So, used half_float::half instead
+using HostReduceDataType = half_float::half;
+
 using ALayout = ck::tensor_layout::gemm::RowMajor;
 using BLayout = ck::tensor_layout::gemm::ColumnMajor;
 using CLayout = ck::tensor_layout::gemm::RowMajor;
@@ -174,18 +178,18 @@ using DeviceElementwiseDivInstance = ck::tensor_operation::device::
 using HostGemmInstance = ck::tensor_operation::host::
     ReferenceGemm<ADataType, BDataType, CDataType, PassThrough, PassThrough, PassThrough>;
 
-using HostReduceMaxInstance = ReductionHost<CDataType,
-                                            CDataType,
-                                            CDataType,
+using HostReduceMaxInstance = ReductionHost<HostReduceDataType,
+                                            HostReduceDataType,
+                                            HostReduceDataType,
                                             ReduceMaxId,
                                             Rank,
                                             NumReduceDim,
                                             ReducePropagateNan,
                                             false>;
 
-using HostReduceSumInstance = ReductionHost<CDataType,
-                                            CDataType,
-                                            CDataType,
+using HostReduceSumInstance = ReductionHost<HostReduceDataType,
+                                            HostReduceDataType,
+                                            HostReduceDataType,
                                             ReduceSumId,
                                             Rank,
                                             NumReduceDim,
@@ -474,18 +478,18 @@ int main(int argc, char* argv[])
 
         host_gemm_invoker.Run(host_gemm_argument);
         host_reduce_max.Run(1, // alpha
-                            reinterpret_cast<const CDataType*>(host_c_m_n.mData.data()),
+                            reinterpret_cast<const HostReduceDataType*>(host_c_m_n.mData.data()),
                             0, // beta
-                            reinterpret_cast<CDataType*>(host_c_n_max.mData.data()),
+                            reinterpret_cast<HostReduceDataType*>(host_c_n_max.mData.data()),
                             host_indices.mData.data());
 
         host_broadcast2D<Tensor<CDataType>, Tensor<CDataType>, Tensor<CDataType>, Sub_Exp, 1>(
             host_exp_m_n, host_c_m_n, host_c_n_max, M, N, Sub_Exp{});
 
         host_reduce_sum.Run(1, // alpha
-                            reinterpret_cast<const CDataType*>(host_exp_m_n.mData.data()),
+                            reinterpret_cast<const HostReduceDataType*>(host_exp_m_n.mData.data()),
                             0, // beta
-                            reinterpret_cast<CDataType*>(host_exp_n_sum.mData.data()),
+                            reinterpret_cast<HostReduceDataType*>(host_exp_n_sum.mData.data()),
                             host_indices.mData.data());
 
         host_broadcast2D<Tensor<CDataType>, Tensor<CDataType>, Tensor<CDataType>, Div, 1>(
@@ -498,15 +502,15 @@ int main(int argc, char* argv[])
         softmax_m_n_device_buf.FromDevice(softmax_m_n.mData.data());
 
         bool result = true;
-        if (result &= ck::utils::check_err(c_m_n.mData, host_c_m_n.mData))
+        if(result &= ck::utils::check_err(c_m_n.mData, host_c_m_n.mData))
             std::cout << "[PASS] - c_m_n" << std::endl;
-        if (result &= ck::utils::check_err(c_n_max.mData, host_c_n_max.mData))
+        if(result &= ck::utils::check_err(c_n_max.mData, host_c_n_max.mData))
             std::cout << "[PASS] - c_n_max" << std::endl;
-        if (result &= ck::utils::check_err(exp_m_n.mData, host_exp_m_n.mData))
+        if(result &= ck::utils::check_err(exp_m_n.mData, host_exp_m_n.mData))
             std::cout << "[PASS] - exp_m_n" << std::endl;
-        if (result &= ck::utils::check_err(exp_n_sum.mData, host_exp_n_sum.mData))
+        if(result &= ck::utils::check_err(exp_n_sum.mData, host_exp_n_sum.mData))
             std::cout << "[PASS] - exp_n_sum" << std::endl;
-        if (result &= ck::utils::check_err(softmax_m_n.mData, host_softmax_m_n.mData))
+        if(result &= ck::utils::check_err(softmax_m_n.mData, host_softmax_m_n.mData))
             std::cout << "[PASS] - softmax_m_n" << std::endl;
     }
     return 0;