SF patch #687598, array.append is sloooow
This improves speed by about 5.6% for me.
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 74934bc..4c1a0fb 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -13,6 +13,52 @@
#endif /* DONT_HAVE_SYS_TYPES_H */
#endif /* !STDC_HEADERS */
+/* Shamelessy stolen from listobject.c */
+static int
+roundupsize(int n)
+{
+ unsigned int nbits = 0;
+ unsigned int n2 = (unsigned int)n >> 5;
+
+ /* Round up:
+ * If n < 256, to a multiple of 8.
+ * If n < 2048, to a multiple of 64.
+ * If n < 16384, to a multiple of 512.
+ * If n < 131072, to a multiple of 4096.
+ * If n < 1048576, to a multiple of 32768.
+ * If n < 8388608, to a multiple of 262144.
+ * If n < 67108864, to a multiple of 2097152.
+ * If n < 536870912, to a multiple of 16777216.
+ * ...
+ * If n < 2**(5+3*i), to a multiple of 2**(3*i).
+ *
+ * This over-allocates proportional to the list size, making room
+ * for additional growth. The over-allocation is mild, but is
+ * enough to give linear-time amortized behavior over a long
+ * sequence of appends() in the presence of a poorly-performing
+ * system realloc() (which is a reality, e.g., across all flavors
+ * of Windows, with Win9x behavior being particularly bad -- and
+ * we've still got address space fragmentation problems on Win9x
+ * even with this scheme, although it requires much longer lists to
+ * provoke them than it used to).
+ */
+ do {
+ n2 >>= 3;
+ nbits += 3;
+ } while (n2);
+ return ((n >> nbits) + 1) << nbits;
+ }
+
+#define NRESIZE(var, type, nitems) \
+do { \
+ size_t _new_size = roundupsize(nitems); \
+ if (_new_size <= ((~(size_t)0) / sizeof(type))) \
+ PyMem_RESIZE(var, type, _new_size); \
+ else \
+ var = NULL; \
+} while (0)
+/* END SHAMELESSLY STOLEN CODE */
+
struct arrayobject; /* Forward */
/* All possible arraydescr values are defined in the vector "descriptors"
@@ -419,8 +465,7 @@
if ((*self->ob_descr->setitem)(self, -1, v) < 0)
return -1;
items = self->ob_item;
- PyMem_RESIZE(items, char,
- (self->ob_size+1) * self->ob_descr->itemsize);
+ NRESIZE(items, char, (self->ob_size+1) * self->ob_descr->itemsize);
if (items == NULL) {
PyErr_NoMemory();
return -1;