math/big: Int slice optimization preliminary benchmarks...

src/pkg/math/big/int_cap.go

Index: src/pkg/math/big/int_cap.go 
=================================================================== 
new file mode 100644 
--- /dev/null 
+++ b/src/pkg/math/big/int_cap.go 
@@ -0,0 +1,49 @@ 
+package big 
+ 
+func (z *Int) SetC(x *Int) *Int { 
+	if z != x { 
+	z.abs = z.abs.setC(x.abs) 
+	z.neg = x.neg 
+	} 
+	return z 
+} 
+ 
+func (z *Int) AddC(x, y *Int) *Int { 
+	neg := x.neg 
+	if x.neg == y.neg { 
+	// x + y == x + y 
+	// (-x) + (-y) == -(x + y) 
+	z.abs = z.abs.addC(x.abs, y.abs) 
+	} else { 
+	panic("not yet implemented") //FIXME 
+	// x + (-y) == x - y == -(y - x) 
+	// (-x) + y == y - x == -(x - y) 
+	if x.abs.cmp(y.abs) >= 0 { 
+	z.abs = z.abs.sub(x.abs, y.abs) 
+	} else { 
+	neg = !neg 
+	z.abs = z.abs.sub(y.abs, x.abs) 
+	} 
+	} 
+	z.neg = len(z.abs) > 0 && neg // 0 has no sign 
+	return z 
+} 
+ 
+func (x *Int) CmpC(y *Int) (r int) { 
+	// x cmp y == x cmp y 
+	// x cmp (-y) == x 
+	// (-x) cmp y == y 
+	// (-x) cmp (-y) == -(x cmp y) 
+	switch { 
+	case x.neg == y.neg: 
+	r = x.abs.cmpC(y.abs) 
+	if x.neg { 
+	r = -r 
+	} 
+	case x.neg: 
+	r = -1 
+	default: 
+	r = 1 
+	} 
+	return 
+}