Question

我正在尝试运行4x4矩阵乘法的C ++函数。 2天后，它终于有效了，但并不像预期的那样。

通常会将参数反馈给函数，然后是这一行：

dataHeap2.set( new Uint8Array(data2.buffer) );

产生错误“Uncaught RangeError：Source is too large”

看起来它看起来只是一个普通的Float32Array，有16个元素，但在查看它的缓冲区大小之后，似乎是不同的

console.log(data2.buffer.bufferLength);

结果不是预期的64字节，而是大数字，如3342345.这是问题吗？我通过手动复制值（如下所示）找到了一种解决方法，返回该值然后问题就消失了。不幸的是，它使我的代码比直接在缓冲区上运行慢得多。

// bad solution - which works
    for(var i = 0; i < 16; i++) {
        dataTarget[i] = result[i];
    }

希望今晚我会找到一个更好的解决方案，我想继续使用这个功能，因为它使用编译的C ++代码，使用ASM.JS + SIMD来解决多个字符。在纯JavaScript中，它仍然太慢。这是整个功能。我很确定data2正在使用Emscripten的HEAP，我希望避免使用它。

matrix4multiply = function(data, data2) {
    // Import function from Emscripten generated file
    var mmul_vec4 = Module.cwrap(
      'mmul_vec4', 'number', ['number', 'number', 'number']
    );

    var dataTarget = new Float32Array(16);

    // Get data byte size, allocate memory on Emscripten heap, and get pointer
    var nDataBytes = dataTarget.length * dataTarget.BYTES_PER_ELEMENT;

    // First matrix copy data to Emscripten heap
    var dataPtr = Module._malloc(nDataBytes);
    var dataPtr2 = Module._malloc(nDataBytes);
    var dataPtr3 = Module._malloc(nDataBytes);

    var dataHeap = new Uint8Array(Module.HEAPU8.buffer, dataPtr, nDataBytes);
    dataHeap.set( new Uint8Array(data.buffer) );

    // second matrix allocate and copy to emscripten's heap
    var dataHeap2 = new Uint8Array(Module.HEAPU8.buffer, dataPtr2, nDataBytes);
    dataHeap2.set( new Uint8Array(data2.buffer) );

    // target heap
    var targetHeap = new Uint8Array(Module.HEAPU8.buffer, dataPtr3, nDataBytes);
    targetHeap.set( new Uint8Array(dataTarget.buffer) );

    // Call the function by passing a number pointing to the byte location of 
    // the array of pointers on the Emscripten heap.  Emscripten knows what to do!
    mmul_vec4(dataHeap.byteOffset, dataHeap2.byteOffset, targetHeap.byteOffset);

    // get result
    var result = new Float32Array(targetHeap.buffer, targetHeap.byteOffset, 16);

    // bad solution - which works
    //for(var i = 0; i < 16; i++) {
    //    dataTarget[i] = result[i];
    //}

    // Free memory
    Module._free(dataHeap.byteOffset);
    Module._free(dataHeap2.byteOffset);
    Module._free(targetHeap.byteOffset);

    return result;
}

编辑：简化版不要担心malloc等

    new Uint8Array(Module.HEAPU8.buffer, this.dataPtr, 64).set( new Uint8Array(data.buffer, data.byteOffset, 64) );

    // second matrix allocate and copy to emscripten's heap
    new Uint8Array(Module.HEAPU8.buffer, this.dataPtr + 72, 64).set( new Uint8Array(data2.buffer, data2.byteOffset, 64) );

    // multiply first two parameters and return in the last one 
    this.mmul_vec4(this.dataPtr, this.dataPtr + 72, this.dataPtr + 144);

    // like that it works, unfotunately copying is being made here
    return new Float32Array(Module.HEAPU8.buffer.slice(this.dataPtr + 144, this.dataPtr + 208));
    // with this version (if uncommented) there's just white screen(but it looks like the game is working.
    //return new Float32Array(Module.HEAPU8.buffer, this.dataPtr + 144, 16);

Answer 1

要使用64位data2字节，请指定偏移量和长度。

dataHeap2.set( new Uint8Array(data2.buffer, data2.byteOffset, nDataBytes) );

Answer 2

这似乎解决了这个问题，但我担心.set功能只能复制数据，而且它不是真正的解决方案。至少比循环克隆更优雅（但它比＃34; Module.HEAPU8.buffer.slice＆＃34;更好）？

matrix4multiplyBlocking = function(data, data2, dataTarget) {
    //console.log(new Float32Array(data2.buffer, data2.byteOffset, 16));
    // Copy data to Emscripten heap
    new Uint8Array(Module.HEAPU8.buffer, this.dataPtr, 64).set( new Uint8Array(data.buffer, data.byteOffset, 64) );

    // second matrix allocate and copy to emscripten's heap
    new Uint8Array(Module.HEAPU8.buffer, this.dataPtr + 72, 64).set( new Uint8Array(data2.buffer, data2.byteOffset, 64) );

    // multiply first two parameters and return in the last one 
    this.mmul_vec4(this.dataPtr, this.dataPtr + 72, this.dataPtr + 144);
    // Free memory
    //Module._free(this.dataPtr);

    dataTarget.set(new Float32Array(Module.HEAPU8.buffer, this.dataPtr + 144, 16));
};

此外，我讨厌创建新的Float32Array实例，因为它会减慢所有内容

Emscripten Uncaught RangeError：源太大，多个Float32Arrays

2 个答案: