Speed up str(int)

As title. Fixes numba#6189
stuartarchibald · Sep 1, 2020 · 3f8ac3e · 3f8ac3e
1 parent d58a63a
commit 3f8ac3e
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Showing 2 changed files with 17 additions and 6 deletions.
diff --git a/numba/cpython/unicode.py b/numba/cpython/unicode.py
@@ -2352,6 +2352,7 @@ def impl(i):
 @overload(str)
 def integer_str(n):
     if isinstance(n, types.Integer):
+
         ten = n(10)
 
         def impl(n):
@@ -2361,16 +2362,23 @@ def impl(n):
                 flag = True
             if n == 0:
                 return '0'
-            l = []
+            length = flag + 1 + int(np.floor(np.log10(n)))
+            kind = PY_UNICODE_1BYTE_KIND
+            char_width = _kind_to_byte_width(kind)
+            s = _malloc_string(kind, char_width, length, True)
+            const = ord('0')
+            if flag:
+                _set_code_point(s, 0, ord('-'))
+            idx = length - 1
             while n > 0:
-                c = chr(ord('0') + (n % ten))
+                c = const + (n % ten)
                 n = n // ten
-                l.append(c)
-            if flag:
-                l.append('-')
-            return ''.join(l[::-1])
+                _set_code_point(s, idx, c)
+                idx -= 1
+            return s
         return impl
 
+
 # ------------------------------------------------------------------------------
 # iteration
 # ------------------------------------------------------------------------------

diff --git a/numba/tests/test_builtins.py b/numba/tests/test_builtins.py
@@ -515,11 +515,14 @@ def test_int_str(self, flags=nrt_no_pyobj_flags):
             1234,
             1,
             0,
+            10,
+            1000,
         ]
 
         large_inputs = [
             123456789,
             2222222,
+            1000000,
             ~0x0
         ]