Enable decimal benchmarks in the suite (MANIFEST)

pyperformance/data-files/benchmarks/MANIFEST

@@ -37,6 +37,8 @@ chaos	<local>
 comprehensions	<local>
 crypto_pyaes	<local>
 dask	<local>
+decimal_factorial	<local>
+decimal_pi	<local>
 deepcopy	<local>
 deltablue	<local>
 django_template	<local>

pyperformance/data-files/benchmarks/bm_decimal_factorial/run_benchmark.py

@@ -4,6 +4,9 @@
 - 2024-06-14: Michael Droettboom copied this from
   Modules/_decimal/tests/bench.py in the CPython source and adapted to use
   pyperf.
+- 2026-02-22: Sergey B Kirpichev adapted context settings and tested
+  values to support also pure-Python decimal module, copy
+  increase_int_max_str_digits() decorator.
 """
 
 # Original copyright notice in CPython source:
@@ -13,9 +16,13 @@
 # Modified and extended by Stefan Krah.
 #
 
-
 import decimal
-
+try:
+    import _decimal
+except ImportError:
+    _decimal = None
+import sys
+from functools import wraps
 
 import pyperf
 
@@ -31,14 +38,32 @@ def factorial(n, m):
         return factorial(n, (n + m) // 2) * factorial((n + m) // 2 + 1, m)
 
 
+def increase_int_max_str_digits(maxdigits):
+    def _increase_int_max_str_digits(func, maxdigits=maxdigits):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            previous_int_limit = sys.get_int_max_str_digits()
+            sys.set_int_max_str_digits(maxdigits)
+            ans = func(*args, **kwargs)
+            sys.set_int_max_str_digits(previous_int_limit)
+            return ans
+        return wrapper
+    return _increase_int_max_str_digits
+
+
+@increase_int_max_str_digits(maxdigits=10000000)
 def bench_decimal_factorial():
     c = decimal.getcontext()
-    c.prec = decimal.MAX_PREC
-    c.Emax = decimal.MAX_EMAX
-    c.Emin = decimal.MIN_EMIN
+    if _decimal:
+        c.prec = decimal.MAX_PREC
+        c.Emax = decimal.MAX_EMAX
+        c.Emin = decimal.MIN_EMIN
+        data = [10000, 100000]
+    else:
+        c.prec = 20000  # Should be enough to hold largest factorial exactly.
+        data = [1000, 5000]
 
-    for n in [10000, 100000]:
-        # C version of decimal
+    for n in data:
         _ = factorial(decimal.Decimal(n), 0)