Improved graph500 performance (Issue #2719)

Author: eholk

src/libcore/vec.rs

@@ -179,7 +179,7 @@ pure fn from_fn<T>(n_elts: uint, op: init_op<T>) -> [T] {
     let mut v = [];
     unchecked{reserve(v, n_elts);}
     let mut i: uint = 0u;
-    while i < n_elts { v += [op(i)]; i += 1u; }
+    while i < n_elts unsafe { push(v, op(i)); i += 1u; }
     ret v;
 }
 
@@ -564,7 +564,7 @@ Apply a function to each element of a vector and return the results
 pure fn mapi<T, U>(v: [T]/&, f: fn(uint, T) -> U) -> [U] {
     let mut result = [];
     unchecked{reserve(result, len(v));}
-    for eachi(v) {|i, elem| result += [f(i, elem)]; }
+    for eachi(v) {|i, elem| unsafe { push(result, f(i, elem)); } }
     ret result;
 }
 

src/libstd/par.rs

@@ -42,7 +42,7 @@ fn map_slices<A: copy send, B: copy send>(
             // FIXME: why is the ::<A, ()> annotation required here? (#2617)
             vec::unpack_slice::<A, ()>(xs) {|p, _len|
                 let f = f();
-                futures += [future::spawn() {|copy base|
+                let f = future::spawn() {|copy base|
                     unsafe {
                         let len = end - base;
                         let slice = (ptr::offset(p, base),
@@ -55,7 +55,8 @@ fn map_slices<A: copy send, B: copy send>(
                         assert(vec::len(slice) == end - base);
                         f(base, slice)
                     }
-                }];
+                };
+                vec::push(futures, f);
             };
             base += items_per_task;
         }

src/test/bench/graph500-bfs.rs

@@ -305,7 +305,7 @@ fn validate(edges: [(node_id, node_id)],
                     status = false;
                 }
 
-                path += [parent];
+                vec::push(path, parent);
                 parent = tree[parent];
             }