GPU上面的除法测试 快速平方根倒数+牛顿迭代

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代码在branch yesx下面

精度请参考程序 https://github.com/konjac/division/blob/yesx/yesx/test.cpp
使用快速平方根倒数得到一个接近的参考值，然后使用牛顿迭代法
自己测了若干数据：
牛顿迭代发的次数，float迭代2次，double迭代3次收敛

速度请参考程序 https://github.com/konjac/division/blob/yesx/gputest-yesx/divisionflops.cu
time = 544.192322 ms

对比的程序为https://github.com/konjac/division/blob/yesx/gputest/divisionflops.cu
time = 748.940674 ms

ARCH = sm_21
实验环境
Device 0: "GeForce GT 630"
CUDA Driver Version / Runtime Version 5.5 / 5.0
CUDA Capability Major/Minor version number: 2.1
Total amount of global memory: 1024 MBytes (1073283072 bytes)
( 2) Multiprocessors x ( 48) CUDA Cores/MP: 96 CUDA Cores
GPU Clock rate: 1620 MHz (1.62 GHz)
Memory Clock rate: 667 Mhz
Memory Bus Width: 128-bit
L2 Cache Size: 131072 bytes
Max Texture Dimension Size (x,y,z) 1D=(65536), 2D=(65536,65535), 3D=(2048,2048,2048)
Max Layered Texture Size (dim) x layers 1D=(16384) x 2048, 2D=(16384,16384) x 2048
Total amount of constant memory: 65536 bytes
Total amount of shared memory per block: 49152 bytes
Total number of registers available per block: 32768
Warp size: 32
Maximum number of threads per multiprocessor: 1536
Maximum number of threads per block: 1024
Maximum sizes of each dimension of a block: 1024 x 1024 x 64
Maximum sizes of each dimension of a grid: 65535 x 65535 x 65535
Maximum memory pitch: 2147483647 bytes
Texture alignment: 512 bytes
Concurrent copy and kernel execution: Yes with 1 copy engine(s)
Run time limit on kernels: Yes
Integrated GPU sharing Host Memory: No
Support host page-locked memory mapping: Yes
Alignment requirement for Surfaces: Yes
Device has ECC support: Disabled
Device supports Unified Addressing (UVA): No
Device PCI Bus ID / PCI location ID: 1 / 0
Compute Mode:
< Default (multiple host threads can use ::cudaSetDevice() with device simultaneously) >

deviceQuery, CUDA Driver = CUDART, CUDA Driver Version = 5.5, CUDA Runtime Version = 5.0, NumDevs = 1, Device0 = GeForce GT 630

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GeForce GT 630

time = 29.137247 ms, Gflops=0.14740