我正在尝试通过F#中两个矩阵的元素乘法来并行化元素。我想不出来的想法。我一直在尝试创建任务,但它永远不想编译。我的非工作杂乱代码如下:
let myBigElemMultiply (m:matrix) (n:matrix) =
let AddTwoRows (row:int) (destination:matrix) (source1:matrix) (source2:matrix) =
for i in 0 .. destination.NumCols
destination.[row, i] <- source1.[row,i] + source2.[row,i]
destination
let result = Matrix.zero(m.NumRows)
let operations = [ for i in 0 .. m.NumRows -> AddTwoRows i result m n ]
let parallelTasks = Async.Parallel operations
Async.RunSynchronously parallelTasks
result
答案 0 :(得分:4)
您犯了几个小错误,例如,您还没有想过如何进行矩阵乘法。
let myBigElemMultiply (m:matrix) (n:matrix) =
let AddTwoRows (row:int) (destination:matrix) (source1:matrix) (source2:matrix) =
for col=0 to destination.NumCols-1 do
let mutable sum = 0.0
for k=0 to m.NumCols-1 do
sum <- sum + source1.[row,k] * source2.[k,col]
destination.[row,col] <- sum
let result = Matrix.zero m.NumRows n.NumCols
let operations = [ for i=0 to m.NumRows-1 do yield async { AddTwoRows i result m n} ]
let parallelTasks = Async.Parallel operations
Async.RunSynchronously parallelTasks |> ignore
result
需要注意的一点是,此代码的执行情况非常糟糕,因为m.[i,j]
是访问矩阵中元素的低效方法。你最好使用2D数组:
let myBigElemMultiply2 (m:matrix) (n:matrix) =
let AddTwoRows (row:int) (destination:matrix) (source1:matrix) (source2:matrix) =
let destination = destination.InternalDenseValues
let source1 = source1.InternalDenseValues
let source2 = source2.InternalDenseValues
for col=0 to Array2D.length2 destination - 1 do
let mutable sum = 0.0
for k=0 to Array2D.length1 source2 - 1 do
sum <- sum + source1.[row,k] * source2.[k,col]
destination.[row,col] <- sum
let result = Matrix.zero m.NumRows n.NumCols
let operations = [ for i=0 to m.NumRows-1 do yield async { AddTwoRows i result m n} ]
let parallelTasks = Async.Parallel operations
Async.RunSynchronously parallelTasks |> ignore
result
测试:
let r = new Random()
let A = Matrix.init 280 10340 (fun i j -> r.NextDouble() )
let B = A.Transpose
某个时间:
> myBigElemMultiply A B;;
Real: 00:00:22.111, CPU: 00:00:41.777, GC gen0: 0, gen1: 0, gen2: 0
val it : unit = ()
> myBigElemMultiply2 A B;;
Real: 00:00:08.736, CPU: 00:00:15.303, GC gen0: 0, gen1: 0, gen2: 0
val it : unit = ()
> A*B;;
Real: 00:00:13.635, CPU: 00:00:13.166, GC gen0: 0, gen1: 0, gen2: 0
val it : unit = ()
>
使用ParallelFor检查here,它应该具有比异步更好的性能。
答案 1 :(得分:2)
这里至少有一些编译的代码,或许这会让你朝着正确的方向前进?
let myBigElemMultiply (m:matrix) (n:matrix) =
let AddTwoRows (row:int) (destination:matrix) (source1:matrix) (source2:matrix) =
async {
for i in 0 .. destination.NumCols do
destination.[row, i] <- source1.[row,i] + source2.[row,i]
}
let result = Matrix.zero m.NumRows m.NumCols
let operations = [ for i in 0 .. m.NumRows -> AddTwoRows i result m n ]
let parallelTasks = Async.Parallel operations
Async.RunSynchronously parallelTasks |> ignore
result
答案 2 :(得分:1)
没有意义。一对矩阵的异地元素乘法更多的是复制,在这一点上,单个核心将愉快地最大化机器的整个内存带宽,并且添加更多核心将不会提高性能。所以几乎可以肯定是浪费时间。