Java 具有特殊类型的Scala优化:长和
我有以下简单的代码Java 具有特殊类型的Scala优化:长和,java,scala,performance,java-stream,bytecode,Java,Scala,Performance,Java Stream,Bytecode,我有以下简单的代码 val longs: Vector[Long] = (1L to 1000000L).toVector 还有所谓的等价Java def jLongs: java.util.stream.LongStream = java.util.stream.LongStream .iterate(1L, (i: Long) => i <= 1000000L, (i: Long) => i + 1L) 所以在我看来,scala版本被迫加载一百万个对象 这就是它
val longs: Vector[Long] = (1L to 1000000L).toVector
还有所谓的等价Java
def jLongs: java.util.stream.LongStream = java.util.stream.LongStream
.iterate(1L, (i: Long) => i <= 1000000L, (i: Long) => i + 1L)
所以在我看来,scala版本被迫加载一百万个对象
这就是它这么慢的原因吗?我怎么能告诉你要专攻长跑
此外,有趣且违反直觉的是,java代码返回一个对象,而在scala中返回一个原语long(参见
ARETURN
vs.LRETURN
)。查看字节码是徒劳的。区别在于流是什么。LongStream
根据需要生成元素。它不是一个数据结构;它是一个控制结构——一个对其他数据源的潜在循环。您的Java可以归结为
var总和:长=0
因为(i查看字节码是徒劳的。区别在于流是什么。长流
按需生成元素。它不是一个数据结构;它是一个控制结构——一个对其他数据源的潜在循环。Java可以归结为
var总和:长=0
对于(我)来说,有没有什么方法可以专门用于long?有没有什么方法可以专门用于long?
@State(Scope.Benchmark)
@BenchmarkMode(Array(Mode.AverageTime))
@OutputTimeUnit(TimeUnit.MILLISECONDS)
class BoxingScala {
val longs: Vector[Long] = (1L to 1000000L).toVector
def jLongs: java.util.stream.LongStream = java.util.stream.LongStream
.iterate(1L, (i: Long) => i <= 1000000L, (i: Long) => i + 1L)
@Benchmark def a: Long = longs.sum
@Benchmark def b: java.lang.Long = jLongs.sum()
}
// access flags 0x1
public a()J
@Lorg/openjdk/jmh/annotations/Benchmark;()
L0
LINENUMBER <benchmark a> L0
ALOAD 0
INVOKEVIRTUAL gurghet/BoxingScala.longs ()Lscala/collection/immutable/Vector;
GETSTATIC scala/math/Numeric$LongIsIntegral$.MODULE$ : Lscala/math/Numeric$LongIsIntegral$;
INVOKEVIRTUAL scala/collection/immutable/Vector.sum (Lscala/math/Numeric;)Ljava/lang/Object;
INVOKESTATIC scala/runtime/BoxesRunTime.unboxToLong (Ljava/lang/Object;)J
LRETURN
L1
LOCALVARIABLE this Lgurghet/BoxingScala; L0 L1 0
MAXSTACK = 2
MAXLOCALS = 1
// access flags 0x1
public b()Ljava/lang/Long;
@Lorg/openjdk/jmh/annotations/Benchmark;()
L0
LINENUMBER <benchmark b> L0
GETSTATIC scala/Predef$.MODULE$ : Lscala/Predef$;
ALOAD 0
INVOKEVIRTUAL gurghet/BoxingScala.jLongs ()Ljava/util/stream/LongStream;
INVOKEINTERFACE java/util/stream/LongStream.sum ()J (itf)
INVOKEVIRTUAL scala/Predef$.long2Long (J)Ljava/lang/Long;
ARETURN
L1
LOCALVARIABLE this Lgurghet/BoxingScala; L0 L1 0
MAXSTACK = 3
MAXLOCALS = 1
L1
LINENUMBER <init> L1
ALOAD 0
NEW scala/runtime/RichLong
DUP
GETSTATIC scala/Predef$.MODULE$ : Lscala/Predef$;
LCONST_1
INVOKEVIRTUAL scala/Predef$.longWrapper (J)J
INVOKESPECIAL scala/runtime/RichLong.<init> (J)V
LDC 1000000
INVOKESTATIC scala/runtime/BoxesRunTime.boxToLong (J)Ljava/lang/Long;
INVOKEVIRTUAL scala/runtime/RichLong.to (Ljava/lang/Object;)Lscala/collection/immutable/NumericRange$Inclusive;
INVOKEVIRTUAL scala/collection/immutable/NumericRange$Inclusive.toVector ()Lscala/collection/immutable/Vector;
PUTFIELD gurghet/BoxingScala.longs : Lscala/collection/immutable/Vector;