Change pow to square in factorization machine layer

paddle/gserver/layers/FactorizationMachineLayer.cpp

@@ -57,12 +57,12 @@ void FactorizationMachineLayer::forward(PassType passType) {
 
   REGISTER_TIMER_INFO("FwMulTimer", getName().c_str());
   tmpMul_->mul(*inputV, *latentVectors_->getW());
-  tmpOut_->pow2(*tmpMul_, 2);
+  tmpMul_->square2(*tmpOut_);
   outV->sumRows(*tmpOut_, 0.5, 0);
 
   x2_ = inputV->clone(0, 0, useGpu_);
-  x2_->pow2(*inputV, 2);
-  v2_->pow2(*latentVectors_->getW(), 2);
+  inputV->square2(*x2_);
+  latentVectors_->getW()->square2(*v2_);
   tmpOut_->mul(*x2_, *v2_);
   outV->sumRows(*tmpOut_, -0.5, 1.0);