更快的方法在C类型转换后复制阵列？ [英] Faster method to copy arrays after typecasting in C?

问题描述

我有一两时二维整数数组 InArray [2] [60] 执行短数据2 LS 2 MS字节字节和位字段数据。请提出一个快速的方法来提取短数据，并将其复制到短 OutArray [60 ] ，东西就行了的memcpy（）。我presume的每个项目迭代是不这样做的最优化方法。
TIA

I have a two-dimesional integer array InArray[2][60] carrying short data in 2 LS bytes and bit field data in 2 MS bytes. Please suggest a faster method to extract short data and copy it to a short OutArray[60], something on the lines for memcpy(). I presume iterating through each item is not the most optimal method of doing this. TIA

编辑：添加code段

int InArray[2][60];
short OutArray[60];
for (int i=0; i < 60;i++)
{
    OutArray[i] = (short)(InArray[0][i] & 0xffff);
}

是否有这样做的更好，更快的可能方式。

Is there a better and possibly faster way of doing this

推荐答案

如果你真的是复制60个元素的数组，那么也没关系。

If you really are copying a 60-element array, then it does not matter.

如果数组是更大和/或你正在做很多次，那么你会想看看的 SIMD 指令集：SSEx在Intel平台上，AltiVec技术在PPC ...

If the array is larger and/or you are doing it a lot of times, then you'll want to have a look at SIMD instruction sets: SSEx on Intel platforms, Altivec on PPC...

例如，使用SSE4，你可以使用_mm_packus_epi32（），它包（和饱和）2 * 4 32位操作数为8个16位操作数。

For instance, using SSE4, you may use _mm_packus_epi32() which packs (and saturates) 2*4 32-bit operands into 8 16-bit operands.

您的编译器可能有内在函数来使用这些： http://msdn.microsoft .COM / EN-US /库/ hh977022.aspx ，的http://gcc.gnu.org/onlinedocs/gcc-3.3.6/gcc/PowerPC-AltiVec-Built_002din-Functions.html...

Your compiler probably has intrinsics to use those: http://msdn.microsoft.com/en-us/library/hh977022.aspx, http://gcc.gnu.org/onlinedocs/gcc-3.3.6/gcc/PowerPC-AltiVec-Built_002din-Functions.html...

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