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好的，所以我已经用所有目标 c 编写了工作代码（是的，我知道 objc 在技术上只是 C。但我的意思是我用消息和东西编写了它。我只有 java 背景，对普通的旧知识不太了解C）但它运行得非常慢。所以我写出了（我认为的）是相同的代码，但是现在这组循环产生了不同的值（仅针对某些数字），而我终其一生都无法弄清楚有什么不同。我正在做的是循环 10 次并在矩阵之间进行 1 次乘法和 1 次加法。我希望有两种语言背景的人可以挑选出我抄错的代码部分。我没有事先对任何数组进行任何更改（这些数组是硬编码的且未受影响），因此 A1、A2 等在代码的两个部分中具有相同的值。

C中的当前代码：

    for (int m = 0; m < 10; m++) {

    //Do matrix multiplication between A1 and A2.  Store in temporary B1
    for( int i = 0; i < 13; i++ )
        for( int j = 0; j < 43; j++ ) {
            double tempTotal = 0;
            for( int k = 0; k < 43; k++){
                tempTotal = tempTotal + A1[i][k] * A2[k][j];
            }
            B1[i][j] = tempTotal;
        }

    //Assign B1 data back into A1 after the multiplication is finished
    for(int i = 0; i < 13; i++)
        for(int j = 0; j<43; j++)
            A1[i][j] = B1[i][j];

    //Add C1 and A1.  Store into C1.
    for (int l = 0; l < 13; l++) 
        for (int n = 0; n < 43; n++) 
            C1[l][n] = C1[l][n] + A1[l][n];

}//end m for loop

这是旧的 Obj c 代码：

 for (int m = 0; m < 10; m++) {
    //multiply A1 and A2.  Store into A1
    A1 = [LCA_Computation multiply:A1 withArray:A2];    //LCA_Computation is the name of the .m class file in which this all happens.  

    //Add C1 and A1.  Store into C1
    for (int i = 0; i < 13; i++) 
        for (int j = 0; j < 43; j++) 
            [[C1 objectAtIndex:i] replaceObjectAtIndex:j withObject:[NSNumber numberWithDouble: [[[C1 objectAtIndex: i] objectAtIndex: j] doubleValue] + [[[A1 objectAtIndex: i] objectAtIndex: j] doubleValue]]];

}//end m for loop

//multiply method
   + (NSMutableArray*)multiply:(NSMutableArray*)a1 withArray:(NSMutableArray*)a2
{
    int a1_rowNum = [a1 count];
    int a2_rowNum = [a2 count];
    int a2_colNum = [[a2 objectAtIndex:0] count];
    NSMutableArray *result = [NSMutableArray arrayWithCapacity:a1_rowNum];
    for (int i = 0; i < a1_rowNum; i++) {
        NSMutableArray *tempRow = [NSMutableArray arrayWithCapacity:a2_colNum];
        for (int j = 0; j < a2_colNum; j++) {
            double tempTotal = 0;
            for (int k = 0; k < a2_rowNum; k++) {
                double temp1 = [[[a1 objectAtIndex:i] objectAtIndex:k] doubleValue];
                double temp2 = [[[a2 objectAtIndex:k] objectAtIndex:j] doubleValue];
                tempTotal += temp1 * temp2;
            }
            //the String format is intentional.  I convert them all to strings later.  I just put it in the method here where as it is done later in the C code
            [tempRow addObject:[NSString stringWithFormat:@"%f",tempTotal]];
        }
        [result addObject:tempRow];
    }
    return result;
}
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1 回答 1

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此问题与先前的内存管理问题有关，导致在某些计算中使用 0。

于 2012-08-07T20:26:20.120 回答