CompareAKMathAgainstMPFR: Add support for the lgamma function

Meta/Lagom/Tools/CompareAKMathAgainstMPFR/main.cpp

@@ -74,6 +74,8 @@ Array g_edge_cases = to_array<double>({ // Denormals
 Array g_exp_perf_ranges = to_array<Range>({ { 0, 1 }, { -10, 10 }, { -745, 709 } });
 Array g_log_perf_ranges = to_array<Range>({ { 0.01, 1 }, { 1, 100 }, { 1, 1e5 } });
 
+Array g_lgamma_perf_ranges = to_array<Range>({ { -100, 0 }, { 0.001, 1 }, { 1, 100 }, { 1, 1e5 } });
+
 Array g_hyperbolic_perf_ranges = to_array<Range>({ { -1, 1 }, { -10, 10 }, { 100, 1e5 } });
 Array g_sinh_perf_ranges = g_hyperbolic_perf_ranges;
 Array g_cosh_perf_ranges = g_hyperbolic_perf_ranges;
@@ -86,6 +88,8 @@ struct RangeWithCount : Range {
 Array g_exp_test_ranges = to_array<RangeWithCount>({ { { -10, 10 }, 150 }, { { -745, 709 }, 50 }, { { -1e-10, 1e-10 }, 50 } });
 Array g_log_test_ranges = to_array<RangeWithCount>({ { { 1e-300, 1 }, 100 }, { { 1, 10 }, 100 }, { { 10, 1e300 }, 50 } });
 
+Array g_lgamma_test_ranges = to_array<RangeWithCount>({ { { -100, 0 }, 150 }, { { 1e-300, 1 }, 100 }, { { 1, 10 }, 100 }, { { 10, 1e300 }, 50 } });
+
 Array g_hyperbolic_test_ranges = to_array<RangeWithCount>({ { { -10, 10 }, 150 }, { { -700, 700 }, 50 }, { { -1e-10, 1e-10 }, 50 } });
 Array g_cosh_test_ranges = g_hyperbolic_test_ranges;
 Array g_sinh_test_ranges = g_hyperbolic_test_ranges;
@@ -117,6 +121,8 @@ Array g_functions = to_array({
     DEFINE_MATH_FUNC(exp),
     DEFINE_MATH_FUNC(log),
 
+    DEFINE_MATH_FUNC(lgamma),
+
     DEFINE_MATH_FUNC(cosh),
     DEFINE_MATH_FUNC(sinh),
     DEFINE_MATH_FUNC(tanh),

Meta/Lagom/Tools/CompareAKMathAgainstMPFR/reference_functions.cpp

@@ -42,6 +42,18 @@ double log(double x)
     return ret;
 }
 
+double lgamma(double x)
+{
+    mpfr_t y;
+    mpfr_init2(y, 53);
+    mpfr_set_d(y, x, MPFR_RNDN);
+    int inex = mpfr_lgamma(y, &signgam, y, MPFR_RNDN);
+    mpfr_subnormalize(y, inex, MPFR_RNDN);
+    double ret = mpfr_get_d(y, MPFR_RNDN);
+    mpfr_clear(y);
+    return ret;
+}
+
 double cosh(double x)
 {
     mpfr_t y;

Meta/Lagom/Tools/CompareAKMathAgainstMPFR/reference_functions.h

@@ -13,6 +13,8 @@ void set_exponent_limits();
 double exp(double x);
 double log(double x);
 
+double lgamma(double x);
+
 double cosh(double x);
 double sinh(double x);
 double tanh(double x);