问尝试为递归函数实现内联Webworker
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Stack Overflow用户

提问于 2018-04-16 15:44:09

回答 2查看 630关注 0票数 0

我有一个使用Javascript的递归函数的第一个版本，它会产生预期的结果。以下是工作版本：

// Call the recursive function and get final (a,b) results
var HitTemp = JSON.parse(JSON.stringify(HitCurrent));
var result= recursiveFunction(HitTemp, HitTemp.playerCurrent, maxNodes);
var a = HitTemp.coordPlayable[0];
var b = HitTemp.coordPlayable[1];

// Recursive function
function recursiveFunction(HitCurrent, colorCurrent, depth) {
 // Indices
 var i, j, k;
 // Evaluation
 var arrayTemp, eval, e;
 // Set current color to HitCurrent
 HitCurrent.playerCurrent = colorCurrent;
 // Deep copy of arrayCurrent array
 arrayTemp = JSON.parse(JSON.stringify(HitCurrent.arrayCurrent));
 // If depth equal to 0
 if (depth == 0)
  return evaluation(HitCurrent);
 // Starting evaluation
 eval = -infinity;
 // Browse all possible hits
 for (i = 0; i < 8; i++)
  for (j = 0; j < 8; j++) {
   if (HitCurrent.arrayPlayable[i][j] == 'playable') {
    for (k = 0; k < 8; k++) {
     // Explore line started from (i,j) with direction "k"
     exploreHitLine(HitCurrent, i, j, k, 'drawing');
    }
    // Recursive call
    e = recursiveFunction(JSON.parse(JSON.stringify(HitCurrent)), ((JSON.stringify(HitCurrent.playerCurrent) == JSON.stringify(playerBlack)) ? playerWhite : playerBlack), depth-1);
    if (e > eval) {
     HitCurrent.coordPlayable = [i,j];
     eval = e;
    }
   }
   // Restore arrayCurrent array
   HitCurrent.arrayCurrent = JSON.parse(JSON.stringify(arrayTemp));
   }
 return eval;
}

从这一点出发，我想使用“内联”WebWorkers将递归专用于WebWorker，并避免在浏览器中挂起进程。

我试着跟踪此链接和另一个链接

我不知道是否必须对主线程"postmessage“对象HitCurrent或值eval：通过使用WebWorker，我在return指令(在终端情况下返回一个值)和传递给下一个递归调用的objetHitCurrent参数之间产生了混淆。

如果有人能给出一些线索，通过使用内联webworker (或者使用webworker的经典方式)来复制这个原始算法。

recursion

web-worker

javascript

回答 2

Stack Overflow用户

回答已采纳

发布于 2018-04-23 22:32:50

内联网络工作者示例：

作为您的代码，没有function evaluation，function exploreHitLine。在使用以下代码之前，必须将它们插入到code中。

{
    let workerScript = URL.createObjectURL( new Blob( [ `
    "use strict";
    // Recursive function
    function recursiveFunction( HitCurrent, colorCurrent, depth ) {
        // Indices
        var i, j, k;
        // Evaluation
        var arrayTemp, eval, e;
        // Set current color to HitCurrent
        HitCurrent.playerCurrent = colorCurrent;
        // Deep copy of arrayCurrent array
        arrayTemp = JSON.parse(JSON.stringify(HitCurrent.arrayCurrent));
        // If depth equal to 0
        if ( depth === 0 ) return evaluation(HitCurrent);
        // Starting evaluation
        eval = -infinity;
        // Browse all possible hits
        for (i = 0; i < 8; i++) {
            for (j = 0; j < 8; j++) {
                if (HitCurrent.arrayPlayable[i][j] === 'playable') {
                    for (k = 0; k < 8; k++) {
                        // Explore line started from (i,j) with direction "k"
                        exploreHitLine(HitCurrent, i, j, k, 'drawing');
                    }
                    // Recursive call
                    e = recursiveFunction(JSON.parse(JSON.stringify(HitCurrent)), ((JSON.stringify(HitCurrent.playerCurrent) == JSON.stringify(playerBlack)) ? playerWhite : playerBlack), depth-1);
                    if (e > eval) {
                        HitCurrent.coordPlayable = [i,j];
                        eval = e;
                    }
                }
                // Restore arrayCurrent array
                HitCurrent.arrayCurrent = JSON.parse(JSON.stringify(arrayTemp));
            }
        }
        return eval;
    }
    onmessage = function ( event ) {
        let params = event.data;
        postMessage( { result: recursiveFunction( ...params ) } );
    }
        ` ], { type: "plain/text" } ) );


    // Call the recursive function and get final (a,b) results
    new Promise( resolve => {
        let HitTemp = JSON.parse(JSON.stringify(HitCurrent));
        let firstWorker = new Worker( workerScript );
        firstWorker.onmessage = function ( event ) {
            resolve( event.data ); //{ result: XXX }
        }
        firstWorker.postMessage( HitTemp, HitTemp.playerCurrent, maxNodes );
    } ).then( ( { result } ) => {
        let [ a, b ] = result.coordPlayable;
        console.log( result );
    } );
}

此外，以下是内联WebWorker：

{
    let workerScript = URL.createObjectURL( new Blob( [ `
    "use strict";
    onmessage = function ( event ) {
        let sum = 0, count = event.data;
        for ( let i = 0; i < count**count; i++ ) {
            sum += i;
        }
        postMessage( { result: sum, count } );
    }
    ` ], { type: "plain/text" } ) );
    let firstWorker = new Worker( workerScript );
    let firstAlive = setTimeout( () => {
        firstWorker.terminate();
        console.log( "terminated" );
    }, 3000 );
    firstWorker.onmessage = function ( event ) {
        clearTimeout( firstAlive );
        console.log( event.data );
    }
    firstWorker.postMessage( 10 );

    let secondWorker = new Worker( workerScript );
    let secondAlive = setTimeout( () => {
        secondWorker.terminate();
        console.log( "terminated" );
    }, 3000 );
    secondWorker.onmessage = function ( event ) {
        clearTimeout( secondAlive );
        console.log( event.data );
    }
    secondWorker.postMessage( 5 );

}

更新1.

{
    // Inline webworker version
    let workerScript = URL.createObjectURL( new Blob( [ `
    "use strict";
    // Recursive function
    function recursiveFunction( HitCurrent, colorCurrent, depth ) {
        // Indices
        var i, j, k;
        // Evaluation
        var arrayTemp, evaluated, e;
        // Set current color to HitCurrent
        HitCurrent.playerCurrent = colorCurrent;
        // Deep copy of arrayCurrent array
        arrayTemp = JSON.parse(JSON.stringify(HitCurrent.arrayCurrent));
        // If depth equal to 0
        if (depth == 0)
        return evaluation(HitCurrent);
        // Starting evaluation
        evaluated = -infinity;
        // Browse all possible hits
        for (i = 0; i < 8; i++) {
            for (j = 0; j < 8; j++) {
                if (HitCurrent.arrayPlayable[i][j] == 'playable') {
                    for (k = 0; k < 8; k++) {
                        // Explore line started from (i,j) with direction "k"
                        exploreHitLine(HitCurrent, i, j, k, 'drawing');
                    }
                    // Recursive call
                    e = recursiveFunction(JSON.parse(JSON.stringify(HitCurrent)), ((JSON.stringify(HitCurrent.playerCurrent) == JSON.stringify(playerBlack)) ? playerWhite : playerBlack), depth-1);
                    if ( e > evaluated ) {
                        HitCurrent.coordPlayable = [i,j];
                        evaluated = e;
                    }
                    if (e == -infinity) { HitCurrent.coordPlayable = [ i, j ]; }
                    // Restore arrayCurrent array
                    HitCurrent.arrayCurrent = JSON.parse(JSON.stringify(arrayTemp));
                }
            }
        }
        return evaluated;
    }

    onmessage = function ( event ) {
        let params = event.data;
        //postMessage( { result: recursiveFunction(  HitCurrent, HitCurrent.playerCurrent, maxNodes ) } );
        postMessage( { result: recursiveFunction( ...params ) } );
    };
    ` ], { type: "plain/text" } ) );


   // Call the recursive function and get final (a,b) results
    new Promise( resolve => {
        let HitTemp = JSON.parse(JSON.stringify(HitCurrent));
        let firstWorker = new Worker( workerScript );
        firstWorker.onmessage = function ( event ) {
            resolve( event.data ); //{ result: XXX }
        }
        firstWorker.postMessage( [ HitTemp, HitTemp.playerCurrent, maxNodes ] );
    } ).then( ( { result } ) => {
        let [ a, b ] = result.coordPlayable;
        console.log( result );
    } );
}

对我错误的解释：

当处于“严格模式”时，不可能使用"eval“作为变量的名称。

来自：eval

致：evaluated

Worker.postMessage( aMessage, Transferrable )，在本例中，您不需要使用第二个参数。

来自：firstWorker.postMessage( HitTemp, HitTemp.playerCurrent, maxNodes );

致：firstWorker.postMessage( [ HitTemp, HitTemp.playerCurrent, maxNodes ] );

(https://developer.mozilla.org/en-US/docs/Web/API/Worker/postMessage)

继续到2，将参数传递给recursiveFunction是固定的。

票数 1

Stack Overflow用户

发布于 2018-04-24 16:52:20

eval是一个关键字；使用其他变量名。
postMessage只接受一个参数(它也接受一个可转移的，但这不适用于您的情况)，如果该参数不是一个原始值，它应该是一个可以序列化的对象(例如，您不能将函数或方法直接传递给web工作者)。

我可能误解了你想要做的事情，但是你可能想重新考虑递归地产生一批不知名的网络工作者！如果您只想释放主堆栈，只需生成一个webworker并将函数的参数传递给它，并在该webworker中同步执行递归计算，而不需要生成一个新的工作人员。产卵太多的网络工作者将消耗大量的资源，实际上会减慢你的计算速度！FYI，产卵每一个新的网络工作者需要40毫秒，并占用资源。这是一个关于使用多线程计算递归函数的一般观察！这可能会有帮助：https://softwareengineering.stackexchange.com/questions/238729/can-recursion-be-done-in-parallel-would-that-make-sense