Update glm invsigmas

Author: Andrew Johnson

stan/math/opencl/prim/normal_id_glm_lpdf.hpp

@@ -99,7 +99,7 @@ return_type_t<T_alpha, T_beta, T_scale> normal_id_glm_lpdf(
   const auto &alpha_val_vec = as_column_vector_or_scalar(alpha_val);
   const auto &sigma_val_vec = to_ref(as_column_vector_or_scalar(sigma_val));
 
-  T_scale_val inv_sigma = 1 / as_array_or_scalar(sigma_val_vec);
+  T_scale_val inv_sigma = 1.0 / as_array_or_scalar(sigma_val_vec);
   Matrix<T_partials_return, Dynamic, 1> y_minus_mu_over_sigma_mat(N);
   auto y_scaled = y_minus_mu_over_sigma_mat.array();
 

stan/math/prim/prob/lognormal_lpdf.hpp

@@ -64,7 +64,7 @@ return_type_t<T_y, T_loc, T_scale> lognormal_lpdf(const T_y& y, const T_loc& mu,
       inv_sigma_sq(size(sigma));
   if (include_summand<propto, T_y, T_loc, T_scale>::value) {
     for (size_t n = 0; n < stan::math::size(sigma); n++) {
-      inv_sigma[n] = inv(value_of(sigma_vec[n]));
+      inv_sigma[n] = 1.0 / value_of(sigma_vec[n]);
     }
   }
   if (include_summand<propto, T_y, T_loc, T_scale>::value) {
@@ -86,7 +86,7 @@ return_type_t<T_y, T_loc, T_scale> lognormal_lpdf(const T_y& y, const T_loc& mu,
       stan::math::size(y));
   if (!is_constant_all<T_y>::value) {
     for (size_t n = 0; n < stan::math::size(y); n++) {
-      inv_y[n] = inv(value_of(y_vec[n]));
+      inv_y[n] = 1.0 / value_of(y_vec[n]);
     }
   }
 

stan/math/prim/prob/normal_id_glm_lpdf.hpp

@@ -100,7 +100,7 @@ return_type_t<T_y, T_x_scalar, T_alpha, T_beta, T_scale> normal_id_glm_lpdf(
   const auto &sigma_val_vec = to_ref(as_column_vector_or_scalar(sigma_val));
   const auto &y_val_vec = as_column_vector_or_scalar(y_val);
 
-  T_scale_val inv_sigma = 1 / as_array_or_scalar(sigma_val_vec);
+  T_scale_val inv_sigma = 1.0 / as_array_or_scalar(sigma_val_vec);
 
   // the most efficient way to calculate this depends on template parameters
   double y_scaled_sq_sum;