Emscripten Uncaught RangeError:源太大,多个Float32Arrays

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,但不如预期的那样.

通常将参数反馈给函数,然后是这一行:

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

产生错误"Uncaught RangeError:Source is too large"

一眼就看起来它只是一个普通的Float32Array,有16个元素,但在查看它的缓冲区大小后,它似乎有所不同

console.log(data2.buffer.bufferLength);

结果不是预期的64字节,而是像3342345这样的巨大数字.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,我想避免它.

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 的头 64 字节data2，请指定偏移量和长度。

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