fix buf of pow bprop

mindspore/ccsrc/pipeline/pynative/pynative_execute.cc

@@ -1185,10 +1185,6 @@ py::tuple RunOp(const py::args &args) {
     std::ostringstream oss;
     trace::TraceGraphEval();
     trace::GetEvalStackInfo(oss);
-    // call py::print to output function call stack to STDOUT, in case of output the log to file, the user can see
-    // these info from screen, no need to open log file to find these info
-    py::print(oss.str());
-    MS_LOG(ERROR) << oss.str();
     PynativeExecutor::GetInstance()->Clean();
     // re-throw this exception to Python interpreter to handle it
     throw(py::error_already_set(ex));

mindspore/ops/_grad/grad_math_ops.py

@@ -526,6 +526,7 @@ def get_bprop_pow(self):
 
     def bprop(x, power, out, dout):
         bc_dx = power * pow_op(x, power - 1.0) * dout
+        x[x < 0] = 1
         bc_dpower = out * ln(x) * dout
         return binop_grad_common(x, power, bc_dx, bc_dpower)