代码级优化(代码质量)

3150阅读　0评论2014-01-18　liubangbo
分类：LINUX

好久没写了，看了一下上次发表的时间是12月14号，今天是1月18号了，一个月多了啊。不找什么借口了，是自己懒惰。 把这几天的工作总结一下：
1. 问题
    要对2048*1080个字节进行内存拷贝工作，当然最简单的就是memcpy来做了，但是由于时间限制，用memcpy耗时太长，需要进行优化。我们是DSP平台，当然提供了快速指令来进行，但是发现时间
    比memcpy还差，这就说明出现问题了，现在把代码贴上(我的代码质量啊...)
   

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  1. #if 0
  2.                         for(i=0; i<2211840; i+=64)
  3.                         {
  4.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i) ,
  5.                                  (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+4),
  6.                                  (unsigned char *)videoPacket->buffers[0].data+i, 0);
  7.                             
  8.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+8),
  9.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+12),
  10.                               (unsigned char *)videoPacket->buffers[0].data+i+8, 0);
  11.                             
  12.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+16),
  13.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+20),
  14.                               (unsigned char *)videoPacket->buffers[0].data+i+16, 0);

  16.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+24),
  17.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+28),
  18.                               (unsigned char *)videoPacket->buffers[0].data+i+24, 0);

  20.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+32) ,
  21.                                  (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+36),
  22.                                  (unsigned char *)videoPacket->buffers[0].data+i+32, 0);
  23.                             
  24.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+40),
  25.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+44),
  26.                               (unsigned char *)videoPacket->buffers[0].data+i+40, 0);
  27.                             
  28.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+48),
  29.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+52),
  30.                               (unsigned char *)videoPacket->buffers[0].data+i+48, 0);

  32.                             SUPER_LD32R((signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+56),
  33.                               (signed long *)(compareSignal.tempMemP[compareSignal.auxFlag]+i+60),
  34.                               (unsigned char *)videoPacket->buffers[0].data+i+56, 0);
  35.                         }
  36.                         #else
  37.                         unsigned char * tempP = compareSignalMem.tempMemP[compareSignal.auxFlag++];
  38.                         unsigned char * tempPacketP = (unsigned char *)videoPacket->buffers[0].data;
  39.                         for(i=0; i<2211840; i+=64)
  40.                         {
  41.                             unsigned char * tempP1 = tempP+i;
  42.                             SUPER_LD32R((signed long *)(tempP1) , (signed long *)(tempP1+4), tempPacketP+i, 0);                            
  43.                             SUPER_LD32R((signed long *)(tempP1+8), (signed long *)(tempP1+12), tempPacketP+i+8, 0);                            
  44.                             SUPER_LD32R((signed long *)(tempP1+16), (signed long *)(tempP1+20), tempPacketP+i+16, 0);
  45.                             SUPER_LD32R((signed long *)(tempP1+24), (signed long *)(tempP1+28), tempPacketP+i+24, 0);
  46.                             SUPER_LD32R((signed long *)(tempP1+32) , (signed long *)(tempP1+36), tempPacketP+i+32, 0);                            
  47.                             SUPER_LD32R((signed long *)(tempP1+40), (signed long *)(tempP1+44), tempPacketP+i+40, 0);                            
  48.                             SUPER_LD32R((signed long *)(tempP1+48), (signed long *)(tempP1+52), tempPacketP+i+48, 0);
  49.                             SUPER_LD32R((signed long *)(tempP1+56), (signed long *)(tempP1+60), tempPacketP+i+56, 0);
  50.                         }
  51.                         #endif
2. 提高代码质量
a) 经测试从内存中取值是非常耗时的，要比运算耗时。所以我在优化后把耗时的compareSignalMem.tempMemP[compareSignal.auxFlag++]; 从for循环中提取了出来，这样耗时减少了。
b)另外还注意了一点就是在一个for循环中多做，减少for循环的次数。当for循环中的运算量比较小，但for循环的次数比较多时，可以采用这个办法来减少for循环的次数。
c)在解决这个问题中，看到从内存中取值还是比较耗时间的


就这样吧

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