diff --git a/Eigen/src/Core/GenericPacketMath.h b/Eigen/src/Core/GenericPacketMath.h
index 8ad51ba..4c7d1d8 100644
--- a/Eigen/src/Core/GenericPacketMath.h
+++ b/Eigen/src/Core/GenericPacketMath.h
@@ -75,6 +75,7 @@
     HasCosh    = 0,
     HasTanh    = 0,
     HasLGamma = 0,
+    HasDiGamma = 0,
     HasErf = 0,
     HasErfc = 0,
 
@@ -439,6 +440,10 @@
 template<typename Packet> EIGEN_DECLARE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS
 Packet plgamma(const Packet& a) { using numext::lgamma; return lgamma(a); }
 
+/** \internal \returns the derivative of lgamma, psi(\a a) (coeff-wise) */
+template<typename Packet> EIGEN_DECLARE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS
+Packet pdigamma(const Packet& a) { using numext::digamma; return digamma(a); }
+
 /** \internal \returns the erf(\a a) (coeff-wise) */
 template<typename Packet> EIGEN_DECLARE_FUNCTION_ALLOWING_MULTIPLE_DEFINITIONS
 Packet perf(const Packet& a) { using numext::erf; return erf(a); }
diff --git a/Eigen/src/Core/GlobalFunctions.h b/Eigen/src/Core/GlobalFunctions.h
index 62fec70..396da8e 100644
--- a/Eigen/src/Core/GlobalFunctions.h
+++ b/Eigen/src/Core/GlobalFunctions.h
@@ -50,6 +50,7 @@
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(cosh,scalar_cosh_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(tanh,scalar_tanh_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(lgamma,scalar_lgamma_op)
+  EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(digamma,scalar_digamma_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(erf,scalar_erf_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(erfc,scalar_erfc_op)
   EIGEN_ARRAY_DECLARE_GLOBAL_UNARY(exp,scalar_exp_op)
diff --git a/Eigen/src/Core/SpecialFunctions.h b/Eigen/src/Core/SpecialFunctions.h
index d43cf23..9fff3d7 100644
--- a/Eigen/src/Core/SpecialFunctions.h
+++ b/Eigen/src/Core/SpecialFunctions.h
@@ -13,79 +13,390 @@
 namespace Eigen {
 namespace internal {
 
+namespace cephes {
+
+/* polevl (modified for Eigen)
+ *
+ *      Evaluate polynomial
+ *
+ *
+ *
+ * SYNOPSIS:
+ *
+ * int N;
+ * Scalar x, y, coef[N+1];
+ *
+ * y = polevl<decltype(x), N>( x, coef);
+ *
+ *
+ *
+ * DESCRIPTION:
+ *
+ * Evaluates polynomial of degree N:
+ *
+ *                     2          N
+ * y  =  C  + C x + C x  +...+ C x
+ *        0    1     2          N
+ *
+ * Coefficients are stored in reverse order:
+ *
+ * coef[0] = C  , ..., coef[N] = C  .
+ *            N                   0
+ *
+ *  The function p1evl() assumes that coef[N] = 1.0 and is
+ * omitted from the array.  Its calling arguments are
+ * otherwise the same as polevl().
+ *
+ *
+ * The Eigen implementation is templatized.  For best speed, store
+ * coef as a const array (constexpr), e.g.
+ *
+ * const double coef[] = {1.0, 2.0, 3.0, ...};
+ *
+ */
+template <typename Scalar, int N>
+struct polevl {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  static Scalar run(const Scalar x, const Scalar coef[]) {
+    EIGEN_STATIC_ASSERT(N > 0, YOU_MADE_A_PROGRAMMING_MISTAKE);
+
+    return polevl<Scalar, N - 1>::run(x, coef) * x + coef[N];
+  }
+};
+
+template <typename Scalar>
+struct polevl<Scalar, 0> {
+  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+  static Scalar run(const Scalar, const Scalar coef[]) {
+    return coef[0];
+  }
+};
+
+}  // end namespace cephes
+
 /****************************************************************************
  * Implementation of lgamma                                                 *
  ****************************************************************************/
 
-template<typename Scalar>
-struct lgamma_impl
-{
+template <typename Scalar>
+struct lgamma_impl {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE Scalar run(const Scalar&)
-  {
+  static EIGEN_STRONG_INLINE Scalar run(const Scalar) {
     EIGEN_STATIC_ASSERT((internal::is_same<Scalar, Scalar>::value == false),
                         THIS_TYPE_IS_NOT_SUPPORTED);
     return Scalar(0);
   }
 };
 
-template<typename Scalar>
-struct lgamma_retval
-{
+template <typename Scalar>
+struct lgamma_retval {
   typedef Scalar type;
 };
 
 #ifdef EIGEN_HAS_C99_MATH
-template<>
-struct lgamma_impl<float>
-{
+template <>
+struct lgamma_impl<float> {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE double run(const float& x) { return ::lgammaf(x); }
+  static EIGEN_STRONG_INLINE float run(float x) { return ::lgammaf(x); }
 };
 
-template<>
-struct lgamma_impl<double>
-{
+template <>
+struct lgamma_impl<double> {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE double run(const double& x) { return ::lgamma(x); }
+  static EIGEN_STRONG_INLINE double run(double x) { return ::lgamma(x); }
 };
 #endif
 
 /****************************************************************************
+ * Implementation of digamma (psi)                                          *
+ ****************************************************************************/
+
+template <typename Scalar>
+struct digamma_impl {
+  EIGEN_DEVICE_FUNC
+  static EIGEN_STRONG_INLINE Scalar run(const Scalar) {
+    EIGEN_STATIC_ASSERT((internal::is_same<Scalar, Scalar>::value == false),
+                        THIS_TYPE_IS_NOT_SUPPORTED);
+    return Scalar(0);
+  }
+};
+
+template <typename Scalar>
+struct digamma_retval {
+  typedef Scalar type;
+};
+
+#ifdef EIGEN_HAS_C99_MATH
+template <>
+struct digamma_impl<float> {
+  /*
+   * Psi (digamma) function (modified for Eigen)
+   *
+   *
+   * SYNOPSIS:
+   *
+   * float x, y, psif();
+   *
+   * y = psif( x );
+   *
+   *
+   * DESCRIPTION:
+   *
+   *              d      -
+   *   psi(x)  =  -- ln | (x)
+   *              dx
+   *
+   * is the logarithmic derivative of the gamma function.
+   * For integer x,
+   *                   n-1
+   *                    -
+   * psi(n) = -EUL  +   >  1/k.
+   *                    -
+   *                   k=1
+   *
+   * If x is negative, it is transformed to a positive argument by the
+   * reflection formula  psi(1-x) = psi(x) + pi cot(pi x).
+   * For general positive x, the argument is made greater than 10
+   * using the recurrence  psi(x+1) = psi(x) + 1/x.
+   * Then the following asymptotic expansion is applied:
+   *
+   *                           inf.   B
+   *                            -      2k
+   * psi(x) = log(x) - 1/2x -   >   -------
+   *                            -        2k
+   *                           k=1   2k x
+   *
+   * where the B2k are Bernoulli numbers.
+   *
+   * ACCURACY:
+   *    Absolute error,  relative when |psi| > 1 :
+   * arithmetic   domain     # trials      peak         rms
+   *    IEEE      -33,0        30000      8.2e-7      1.2e-7
+   *    IEEE      0,33        100000      7.3e-7      7.7e-8
+   *
+   * ERROR MESSAGES:
+   *     message         condition      value returned
+   * psi singularity    x integer <=0      INFINITY
+   */
+  /*
+    Cephes Math Library Release 2.2:  June, 1992
+    Copyright 1984, 1987, 1992 by Stephen L. Moshier
+    Direct inquiries to 30 Frost Street, Cambridge, MA 02140
+  */
+  EIGEN_DEVICE_FUNC
+  static float run(float xx) {
+    float p, q, nz, x, s, w, y, z;
+    bool negative;
+
+    // Some necessary constants
+    const float PIF = 3.141592653589793238;
+    const float MAXNUMF = std::numeric_limits<float>::infinity();
+
+    const float A[] = {
+      -4.16666666666666666667E-3,
+      3.96825396825396825397E-3,
+      -8.33333333333333333333E-3,
+      8.33333333333333333333E-2
+    };
+
+    x = xx;
+    nz = 0.0f;
+    negative = 0;
+    if (x <= 0.0f) {
+      negative = 1;
+      q = x;
+      p = ::floor(q);
+      if (p == q) {
+        return (MAXNUMF);
+      }
+      nz = q - p;
+      if (nz != 0.5f) {
+        if (nz > 0.5f) {
+          p += 1.0f;
+          nz = q - p;
+        }
+        nz = PIF / ::tan(PIF * nz);
+      } else {
+        nz = 0.0f;
+      }
+      x = 1.0f - x;
+    }
+
+    /* use the recurrence psi(x+1) = psi(x) + 1/x. */
+    s = x;
+    w = 0.0f;
+    while (s < 10.0f) {
+      w += 1.0f / s;
+      s += 1.0f;
+    }
+
+    if (s < 1.0e8f) {
+      z = 1.0f / (s * s);
+      y = z * cephes::polevl<float, 3>::run(z, A);
+    } else
+      y = 0.0f;
+
+    y = ::log(s) - (0.5f / s) - y - w;
+
+    return (negative) ? y - nz : y;
+  }
+};
+
+template <>
+struct digamma_impl<double> {
+  EIGEN_DEVICE_FUNC
+  static double run(double x) {
+    /*
+     *
+     *     Psi (digamma) function (modified for Eigen)
+     *
+     *
+     * SYNOPSIS:
+     *
+     * double x, y, psi();
+     *
+     * y = psi( x );
+     *
+     *
+     * DESCRIPTION:
+     *
+     *              d      -
+     *   psi(x)  =  -- ln | (x)
+     *              dx
+     *
+     * is the logarithmic derivative of the gamma function.
+     * For integer x,
+     *                   n-1
+     *                    -
+     * psi(n) = -EUL  +   >  1/k.
+     *                    -
+     *                   k=1
+     *
+     * If x is negative, it is transformed to a positive argument by the
+     * reflection formula  psi(1-x) = psi(x) + pi cot(pi x).
+     * For general positive x, the argument is made greater than 10
+     * using the recurrence  psi(x+1) = psi(x) + 1/x.
+     * Then the following asymptotic expansion is applied:
+     *
+     *                           inf.   B
+     *                            -      2k
+     * psi(x) = log(x) - 1/2x -   >   -------
+     *                            -        2k
+     *                           k=1   2k x
+     *
+     * where the B2k are Bernoulli numbers.
+     *
+     * ACCURACY:
+     *    Relative error (except absolute when |psi| < 1):
+     * arithmetic   domain     # trials      peak         rms
+     *    IEEE      0,30        30000       1.3e-15     1.4e-16
+     *    IEEE      -30,0       40000       1.5e-15     2.2e-16
+     *
+     * ERROR MESSAGES:
+     *     message         condition      value returned
+     * psi singularity    x integer <=0      INFINITY
+     */
+
+    /*
+     * Cephes Math Library Release 2.8:  June, 2000
+     * Copyright 1984, 1987, 1992, 2000 by Stephen L. Moshier
+     */
+    double p, q, nz, s, w, y, z;
+    bool negative;
+
+    const double A[] = {
+      8.33333333333333333333E-2,
+      -2.10927960927960927961E-2,
+      7.57575757575757575758E-3,
+      -4.16666666666666666667E-3,
+      3.96825396825396825397E-3,
+      -8.33333333333333333333E-3,
+      8.33333333333333333333E-2
+    };
+
+    const double MAXNUM = std::numeric_limits<double>::infinity();
+    const double PI = 3.14159265358979323846;
+
+    negative = 0;
+    nz = 0.0;
+
+    if (x <= 0.0) {
+      negative = 1;
+      q = x;
+      p = ::floor(q);
+      if (p == q) {
+        return MAXNUM;
+      }
+      /* Remove the zeros of tan(PI x)
+       * by subtracting the nearest integer from x
+       */
+      nz = q - p;
+      if (nz != 0.5) {
+        if (nz > 0.5) {
+          p += 1.0;
+          nz = q - p;
+        }
+        nz = PI / ::tan(PI * nz);
+      }
+      else {
+        nz = 0.0;
+      }
+      x = 1.0 - x;
+    }
+
+    /* use the recurrence psi(x+1) = psi(x) + 1/x. */
+    s = x;
+    w = 0.0;
+    while (s < 10.0) {
+      w += 1.0 / s;
+      s += 1.0;
+    }
+
+    if (s < 1.0e17) {
+      z = 1.0 / (s * s);
+      y = z * cephes::polevl<double, 6>::run(z, A);
+    }
+    else
+      y = 0.0;
+
+    y = ::log(s) - (0.5 / s) - y - w;
+
+    return (negative) ? y - nz : y;
+  }
+};
+
+#endif
+
+/****************************************************************************
  * Implementation of erf                                                    *
  ****************************************************************************/
 
-template<typename Scalar>
-struct erf_impl
-{
+template <typename Scalar>
+struct erf_impl {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE Scalar run(const Scalar&)
-  {
+  static EIGEN_STRONG_INLINE Scalar run(const Scalar) {
     EIGEN_STATIC_ASSERT((internal::is_same<Scalar, Scalar>::value == false),
                         THIS_TYPE_IS_NOT_SUPPORTED);
     return Scalar(0);
   }
 };
 
-template<typename Scalar>
-struct erf_retval
-{
+template <typename Scalar>
+struct erf_retval {
   typedef Scalar type;
 };
 
 #ifdef EIGEN_HAS_C99_MATH
-template<>
-struct erf_impl<float>
-{
+template <>
+struct erf_impl<float> {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE float run(const float& x) { return ::erff(x); }
+  static EIGEN_STRONG_INLINE float run(float x) { return ::erff(x); }
 };
 
-template<>
-struct erf_impl<double>
-{
+template <>
+struct erf_impl<double> {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE double run(const double& x) { return ::erf(x); }
+  static EIGEN_STRONG_INLINE double run(double x) { return ::erf(x); }
 };
 #endif  // EIGEN_HAS_C99_MATH
 
@@ -93,35 +404,30 @@
 * Implementation of erfc                                                   *
 ****************************************************************************/
 
-template<typename Scalar>
-struct erfc_impl
-{
+template <typename Scalar>
+struct erfc_impl {
   EIGEN_DEVICE_FUNC
-  static EIGEN_STRONG_INLINE Scalar run(const Scalar&)
-  {
+  static EIGEN_STRONG_INLINE Scalar run(const Scalar) {
     EIGEN_STATIC_ASSERT((internal::is_same<Scalar, Scalar>::value == false),
                         THIS_TYPE_IS_NOT_SUPPORTED);
     return Scalar(0);
   }
 };
 
-template<typename Scalar>
-struct erfc_retval
-{
+template <typename Scalar>
+struct erfc_retval {
   typedef Scalar type;
 };
 
 #ifdef EIGEN_HAS_C99_MATH
-template<>
-struct erfc_impl<float>
-{
+template <>
+struct erfc_impl<float> {
   EIGEN_DEVICE_FUNC
   static EIGEN_STRONG_INLINE float run(const float x) { return ::erfcf(x); }
 };
 
-template<>
-struct erfc_impl<double>
-{
+template <>
+struct erfc_impl<double> {
   EIGEN_DEVICE_FUNC
   static EIGEN_STRONG_INLINE double run(const double x) { return ::erfc(x); }
 };
@@ -129,27 +435,29 @@
 
 }  // end namespace internal
 
-
 namespace numext {
 
-template<typename Scalar>
-EIGEN_DEVICE_FUNC
-inline EIGEN_MATHFUNC_RETVAL(lgamma, Scalar) lgamma(const Scalar& x)
-{
+template <typename Scalar>
+EIGEN_DEVICE_FUNC inline EIGEN_MATHFUNC_RETVAL(lgamma, Scalar)
+    lgamma(const Scalar& x) {
   return EIGEN_MATHFUNC_IMPL(lgamma, Scalar)::run(x);
 }
 
-template<typename Scalar>
-EIGEN_DEVICE_FUNC
-inline EIGEN_MATHFUNC_RETVAL(erf, Scalar) erf(const Scalar& x)
-{
+template <typename Scalar>
+EIGEN_DEVICE_FUNC inline EIGEN_MATHFUNC_RETVAL(digamma, Scalar)
+    digamma(const Scalar& x) {
+  return EIGEN_MATHFUNC_IMPL(digamma, Scalar)::run(x);
+}
+
+template <typename Scalar>
+EIGEN_DEVICE_FUNC inline EIGEN_MATHFUNC_RETVAL(erf, Scalar)
+    erf(const Scalar& x) {
   return EIGEN_MATHFUNC_IMPL(erf, Scalar)::run(x);
 }
 
-template<typename Scalar>
-EIGEN_DEVICE_FUNC
-inline EIGEN_MATHFUNC_RETVAL(erfc, Scalar) erfc(const Scalar& x)
-{
+template <typename Scalar>
+EIGEN_DEVICE_FUNC inline EIGEN_MATHFUNC_RETVAL(erfc, Scalar)
+    erfc(const Scalar& x) {
   return EIGEN_MATHFUNC_IMPL(erfc, Scalar)::run(x);
 }
 
diff --git a/Eigen/src/Core/arch/CUDA/MathFunctions.h b/Eigen/src/Core/arch/CUDA/MathFunctions.h
index ecd5c44..a2c06a8 100644
--- a/Eigen/src/Core/arch/CUDA/MathFunctions.h
+++ b/Eigen/src/Core/arch/CUDA/MathFunctions.h
@@ -79,6 +79,20 @@
 }
 
 template<> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+float4 pdigamma<float4>(const float4& a)
+{
+  using numext::digamma;
+  return make_float4(digamma(a.x), digamma(a.y), digamma(a.z), digamma(a.w));
+}
+
+template<> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
+double2 pdigamma<double2>(const double2& a)
+{
+  using numext::digamma;
+  return make_double2(digamma(a.x), digamma(a.y));
+}
+
+template<> EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
 float4 perf<float4>(const float4& a)
 {
   return make_float4(erf(a.x), erf(a.y), erf(a.z), erf(a.w));
diff --git a/Eigen/src/Core/arch/CUDA/PacketMath.h b/Eigen/src/Core/arch/CUDA/PacketMath.h
index 9d57731..d3d9f91 100644
--- a/Eigen/src/Core/arch/CUDA/PacketMath.h
+++ b/Eigen/src/Core/arch/CUDA/PacketMath.h
@@ -40,6 +40,7 @@
     HasSqrt = 1,
     HasRsqrt = 1,
     HasLGamma = 1,
+    HasDiGamma = 1,
     HasErf = 1,
     HasErfc = 1,
 
@@ -63,6 +64,7 @@
     HasSqrt = 1,
     HasRsqrt = 1,
     HasLGamma = 1,
+    HasDiGamma = 1,
     HasErf = 1,
     HasErfc = 1,
 
diff --git a/Eigen/src/Core/functors/UnaryFunctors.h b/Eigen/src/Core/functors/UnaryFunctors.h
index 01727f2..897ab04 100644
--- a/Eigen/src/Core/functors/UnaryFunctors.h
+++ b/Eigen/src/Core/functors/UnaryFunctors.h
@@ -428,6 +428,28 @@
 };
 
 /** \internal
+ * \brief Template functor to compute psi, the derivative of lgamma of a scalar.
+ * \sa class CwiseUnaryOp, Cwise::digamma()
+ */
+template<typename Scalar> struct scalar_digamma_op {
+  EIGEN_EMPTY_STRUCT_CTOR(scalar_digamma_op)
+  EIGEN_DEVICE_FUNC inline const Scalar operator() (const Scalar& a) const {
+    using numext::digamma; return digamma(a);
+  }
+  typedef typename packet_traits<Scalar>::type Packet;
+  EIGEN_DEVICE_FUNC inline Packet packetOp(const Packet& a) const { return internal::pdigamma(a); }
+};
+template<typename Scalar>
+struct functor_traits<scalar_digamma_op<Scalar> >
+{
+  enum {
+    // Guesstimate
+    Cost = 10 * NumTraits<Scalar>::MulCost + 5 * NumTraits<Scalar>::AddCost,
+    PacketAccess = packet_traits<Scalar>::HasDiGamma
+  };
+};
+
+/** \internal
  * \brief Template functor to compute the Gauss error function of a
  * scalar
  * \sa class CwiseUnaryOp, Cwise::erf()
diff --git a/Eigen/src/plugins/ArrayCwiseUnaryOps.h b/Eigen/src/plugins/ArrayCwiseUnaryOps.h
index 01432e2..e818ac5 100644
--- a/Eigen/src/plugins/ArrayCwiseUnaryOps.h
+++ b/Eigen/src/plugins/ArrayCwiseUnaryOps.h
@@ -22,6 +22,7 @@
 typedef CwiseUnaryOp<internal::scalar_sinh_op<Scalar>, const Derived> SinhReturnType;
 typedef CwiseUnaryOp<internal::scalar_cosh_op<Scalar>, const Derived> CoshReturnType;
 typedef CwiseUnaryOp<internal::scalar_lgamma_op<Scalar>, const Derived> LgammaReturnType;
+typedef CwiseUnaryOp<internal::scalar_digamma_op<Scalar>, const Derived> DigammaReturnType;
 typedef CwiseUnaryOp<internal::scalar_erf_op<Scalar>, const Derived> ErfReturnType;
 typedef CwiseUnaryOp<internal::scalar_erfc_op<Scalar>, const Derived> ErfcReturnType;
 typedef CwiseUnaryOp<internal::scalar_pow_op<Scalar>, const Derived> PowReturnType;
@@ -318,6 +319,19 @@
   return LgammaReturnType(derived());
 }
 
+/** \returns an expression of the coefficient-wise digamma (psi, derivative of lgamma).
+ *
+ * Example: \include Cwise_digamma.cpp
+ * Output: \verbinclude Cwise_digamma.out
+ *
+ * \sa cos(), sin(), tan()
+ */
+inline const DigammaReturnType
+digamma() const
+{
+  return DigammaReturnType(derived());
+}
+
 /** \returns an expression of the coefficient-wise Gauss error
  * function of *this.
  *