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[Math] Remove ROOT::Math::digamma() function #21970

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Merged
guitargeek merged 1 commit into from
Apr 20, 2026
+9 −39
Merged

[Math] Remove ROOT::Math::digamma() function #21970

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37 changes: 9 additions & 28 deletions math/mathcore/inc/Math/CladDerivator.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,13 +25,6 @@
#include <plugins/include/clad/Differentiator/Differentiator.h>
#include "TMath.h"

// For the digamma function, that is the derivative of lgamma. We get it via
// mathmore from the GSL, so the pullbacks that use digamma are only available
// with mathmore=ON.
#ifdef R__HAS_MATHMORE
#include "Math/SpecFuncMathMore.h"
#endif

#include <stdexcept>

namespace clad {
Expand Down Expand Up @@ -103,16 +96,12 @@ ValueAndPushforward<T, T> Erfc_pushforward(T x, T d_x)
return {::TMath::Erfc(x), -Erf_pushforward(x, d_x).pushforward};
}

#ifdef R__HAS_MATHMORE

template <typename T>
ValueAndPushforward<T, T> LnGamma_pushforward(T z, T d_z)
{
return {::TMath::LnGamma(z), ::ROOT::Math::digamma(z) * d_z};
return {::TMath::LnGamma(z), ::clad::custom_derivatives::std::clad_digamma(z) * d_z};
}

#endif

template <typename T>
ValueAndPushforward<T, T> Exp_pushforward(T x, T d_x)
{
Expand Down Expand Up @@ -633,8 +622,6 @@ inline void landau_cdf_pullback(double x, double xi, double x0, double d_out, do
*d_xi += _d_v * -((x - x0) / (xi * xi));
}

#ifdef R__HAS_MATHMORE

inline void inc_gamma_c_pullback(double a, double x, double _d_y, double *_d_a, double *_d_x);

inline void inc_gamma_pullback(double a, double x, double _d_y, double *_d_a, double *_d_x)
Expand Down Expand Up @@ -674,9 +661,8 @@ inline void inc_gamma_pullback(double a, double x, double _d_y, double *_d_a, do
ax = a * _t1 - x - ::std::lgamma(a);
if (ax < -kMAXLOG) {
*_d_x += (a * _d_ax / x) - _d_ax;
*_d_a +=
_d_ax *
(_t1 - ::ROOT::Math::digamma(a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
*_d_a += _d_ax * (_t1 - ::clad::custom_derivatives::std::clad_digamma(
a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
_d_ax = 0.;
return;
}
Expand Down Expand Up @@ -753,9 +739,8 @@ inline void inc_gamma_pullback(double a, double x, double _d_y, double *_d_a, do
}
{
*_d_x += (a * _d_ax / x) - _d_ax;
*_d_a +=
_d_ax *
(_t1 - ::ROOT::Math::digamma(a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
*_d_a += _d_ax * (_t1 - ::clad::custom_derivatives::std::clad_digamma(
a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
_d_ax = 0.;
}
}
Expand Down Expand Up @@ -822,9 +807,8 @@ inline void inc_gamma_c_pullback(double a, double x, double _d_y, double *_d_a,
ax = a * _t1 - x - ::std::lgamma(a);
if (ax < -kMAXLOG) {
*_d_x += a * _d_ax / x - _d_ax;
*_d_a +=
_d_ax *
(_t1 - ::ROOT::Math::digamma(a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
*_d_a += _d_ax * (_t1 - ::clad::custom_derivatives::std::clad_digamma(
a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
_d_ax = 0.;
return;
}
Expand Down Expand Up @@ -1085,15 +1069,12 @@ inline void inc_gamma_c_pullback(double a, double x, double _d_y, double *_d_a,
}
{
*_d_x += a * _d_ax / x - _d_ax;
*_d_a +=
_d_ax *
(_t1 - ::ROOT::Math::digamma(a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
*_d_a += _d_ax * (_t1 - ::clad::custom_derivatives::std::clad_digamma(
a)); // numerical_diff::forward_central_difference(::std::lgamma, a, 0, 0, a);
_d_ax = 0.;
}
}

#endif // R__HAS_MATHMORE

} // namespace Math
} // namespace ROOT

Expand Down
3 changes: 0 additions & 3 deletions math/mathmore/inc/Math/SpecFuncMathMore.h
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Original file line number Diff line number Diff line change
Expand Up @@ -873,9 +873,6 @@ namespace Math {

double wigner_9j(int two_ja, int two_jb, int two_jc, int two_jd, int two_je, int two_jf, int two_jg, int two_jh, int two_ji);

double digamma(double x);


} // namespace Math
} // namespace ROOT

Expand Down
8 changes: 0 additions & 8 deletions math/mathmore/src/SpecFuncMathMore.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,6 @@
#include "gsl/gsl_sf_zeta.h"
#include "gsl/gsl_sf_airy.h"
#include "gsl/gsl_sf_coupling.h"
#include "gsl/gsl_sf_psi.h"


namespace ROOT {
Expand Down Expand Up @@ -475,12 +474,5 @@ double wigner_9j(int ja, int jb, int jc, int jd, int je, int jf, int jg, int jh,
return gsl_sf_coupling_9j(ja,jb,jc,jd,je,jf,jg,jh,ji);
}

// Psi (Digamma) Function.

double digamma(double x)
{
return gsl_sf_psi(x);
}

} // namespace Math
} // namespace ROOT
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