Mix fixes

Author: andrjohns

stan/math/fwd/fun/log1m_inv_logit.hpp

@@ -20,7 +20,7 @@ namespace math {
 template <typename T>
 inline fvar<T> log1m_inv_logit(const fvar<T>& x) {
   using std::exp;
-  return fvar<T>(log1m_inv_logit(x.val_), -x.d_ / (1 + exp(-x.val_)));
+  return fvar<T>(log1m_inv_logit(x.val_), -x.d_ * inv_logit(x.val_));
 }
 
 }  // namespace math

stan/math/fwd/fun/log1p_exp.hpp

@@ -12,7 +12,7 @@ namespace math {
 template <typename T>
 inline fvar<T> log1p_exp(const fvar<T>& x) {
   using std::exp;
-  return fvar<T>(log1p_exp(x.val_), x.d_ / (1 + exp(-x.val_)));
+  return fvar<T>(log1p_exp(x.val_), x.d_ * inv_logit(x.val_));
 }
 
 }  // namespace math

stan/math/fwd/fun/log_inv_logit.hpp

@@ -3,6 +3,7 @@
 
 #include <stan/math/fwd/meta.hpp>
 #include <stan/math/fwd/core.hpp>
+#include <stan/math/prim/fun/inv_logit.hpp>
 #include <stan/math/prim/fun/log_inv_logit.hpp>
 #include <cmath>
 
@@ -12,7 +13,7 @@ namespace math {
 template <typename T>
 inline fvar<T> log_inv_logit(const fvar<T>& x) {
   using std::exp;
-  return fvar<T>(log_inv_logit(x.val_), x.d_ / (1 + exp(x.val_)));
+  return fvar<T>(log_inv_logit(x.val_), x.d_ * inv_logit(-x.val_));
 }
 }  // namespace math
 }  // namespace stan

stan/math/fwd/fun/log_sum_exp.hpp

@@ -18,8 +18,8 @@ template <typename T>
 inline fvar<T> log_sum_exp(const fvar<T>& x1, const fvar<T>& x2) {
   using std::exp;
   return fvar<T>(log_sum_exp(x1.val_, x2.val_),
-                 x1.d_ / (1 + exp(x2.val_ - x1.val_))
-                     + x2.d_ / (exp(x1.val_ - x2.val_) + 1));
+                 x1.d_ * inv_logit(-(x2.val_ - x1.val_))
+                     + x2.d_ * inv_logit(-(x1.val_ - x2.val_)));
 }
 
 template <typename T>
@@ -28,7 +28,7 @@ inline fvar<T> log_sum_exp(double x1, const fvar<T>& x2) {
   if (x1 == NEGATIVE_INFTY) {
     return fvar<T>(x2.val_, x2.d_);
   }
-  return fvar<T>(log_sum_exp(x1, x2.val_), x2.d_ / (exp(x1 - x2.val_) + 1));
+  return fvar<T>(log_sum_exp(x1, x2.val_), x2.d_ * inv_logit(-(x1 - x2.val_)));
 }
 
 template <typename T>

stan/math/prim/prob/logistic_cdf.hpp

@@ -10,6 +10,7 @@
 #include <stan/math/prim/fun/size.hpp>
 #include <stan/math/prim/fun/size_zero.hpp>
 #include <stan/math/prim/fun/value_of.hpp>
+#include <stan/math/prim/fun/inv_logit.hpp>
 #include <stan/math/prim/prob/logistic_log.hpp>
 #include <stan/math/prim/functor/partials_propagator.hpp>
 #include <cmath>
@@ -70,8 +71,8 @@ return_type_t<T_y, T_loc, T_scale> logistic_cdf(const T_y& y, const T_loc& mu,
     const T_partials_return sigma_dbl = sigma_vec.val(n);
     const T_partials_return sigma_inv_vec = 1.0 / sigma_vec.val(n);
 
-    const T_partials_return Pn
-        = 1.0 / (1.0 + exp(-(y_dbl - mu_dbl) * sigma_inv_vec));
+    // TODO(Andrew) Further simplify derivatives and log scale below
+    const T_partials_return Pn = inv_logit((y_dbl - mu_dbl) * sigma_inv_vec);
 
     P *= Pn;
 

stan/math/prim/prob/logistic_lccdf.hpp

@@ -6,6 +6,7 @@
 #include <stan/math/prim/fun/constants.hpp>
 #include <stan/math/prim/fun/exp.hpp>
 #include <stan/math/prim/fun/log.hpp>
+#include <stan/math/prim/fun/inv_logit.hpp>
 #include <stan/math/prim/fun/max_size.hpp>
 #include <stan/math/prim/fun/scalar_seq_view.hpp>
 #include <stan/math/prim/fun/size.hpp>
@@ -71,8 +72,9 @@ return_type_t<T_y, T_loc, T_scale> logistic_lccdf(const T_y& y, const T_loc& mu,
     const T_partials_return sigma_dbl = sigma_vec.val(n);
     const T_partials_return sigma_inv_vec = 1.0 / sigma_vec.val(n);
 
+    // TODO(Andrew) Further simplify derivatives and log-scale below
     const T_partials_return Pn
-        = 1.0 - 1.0 / (1.0 + exp(-(y_dbl - mu_dbl) * sigma_inv_vec));
+        = 1.0 - inv_logit((y_dbl - mu_dbl) * sigma_inv_vec);
     P += log(Pn);
 
     if (!is_constant_all<T_y>::value) {

stan/math/prim/prob/logistic_lcdf.hpp

@@ -6,6 +6,7 @@
 #include <stan/math/prim/fun/constants.hpp>
 #include <stan/math/prim/fun/exp.hpp>
 #include <stan/math/prim/fun/log.hpp>
+#include <stan/math/prim/fun/inv_logit.hpp>
 #include <stan/math/prim/fun/scalar_seq_view.hpp>
 #include <stan/math/prim/fun/max_size.hpp>
 #include <stan/math/prim/fun/size.hpp>
@@ -71,8 +72,8 @@ return_type_t<T_y, T_loc, T_scale> logistic_lcdf(const T_y& y, const T_loc& mu,
     const T_partials_return sigma_dbl = sigma_vec.val(n);
     const T_partials_return sigma_inv_vec = 1.0 / sigma_vec.val(n);
 
-    const T_partials_return Pn
-        = 1.0 / (1.0 + exp(-(y_dbl - mu_dbl) * sigma_inv_vec));
+    // TODO(Andrew) Further simplify derivatives and log-scale below
+    const T_partials_return Pn = inv_logit((y_dbl - mu_dbl) * sigma_inv_vec);
     P += log(Pn);
 
     if (!is_constant_all<T_y>::value) {