optimize reserve vec for imul

qingshi163 · qingshi163 · commit 878f52bdbe66 · 2021-11-22T08:13:03.000+02:00
diff --git a/vm/src/sequence.rs b/vm/src/sequence.rs
@@ -272,6 +272,7 @@ pub trait SequenceMutOp<T: Clone> {
         } else if n != 1 {
             let mut sample = self.as_slice().to_vec();
             if n != 2 {
+                self.as_vec_mut().reserve(sample.len() * (n - 1));
                 for _ in 0..n - 2 {
                     self.as_vec_mut().extend_from_slice(&sample);
                 }

Original file line number	Diff line number	Diff line change
`@@ -272,6 +272,7 @@ pub trait SequenceMutOp<T: Clone> {`
`272`	`272`	`} else if n != 1 {`
`273`	`273`	`let mut sample = self.as_slice().to_vec();`
`274`	`274`	`if n != 2 {`
	`275`	`+ self.as_vec_mut().reserve(sample.len() * (n - 1));`
`275`	`276`	`for _ in 0..n - 2 {`
`276`	`277`	`self.as_vec_mut().extend_from_slice(&sample);`
`277`	`278`	`}`