add readme

README.md

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+Genie and Lamp GPU
+===
+
+### Milestone:
+
+* Finish GPU and GPU SCAN with CUDA. And the the top K is selected by ***bucket algorithm***. Details can be found in [https://github.com/imwithye/CUDA-K-Nearest-Neighbors](https://github.com/imwithye/CUDA-K-Nearest-Neighbors). Bucket selection algorithm is published on [http://www.math.grinnell.edu/~blanchaj/Research/Research.html#ggkspaper](http://www.math.grinnell.edu/~blanchaj/Research/Research.html#ggkspaper) and implemented by [Yiwei](http://github.com/imwithye), imwithye@gmail.com
+
+* Finish CPU SCAN algorithm
+
+---
+
+### Running test case:
+
+***Note: Build this project in nsight release mode!***
+
+#### Command line arguments:
+
+1. `--topk` or `-k` sets the value of K. Default value is 128
+2. `--dimension` or `-d` sets the value of dimension number. Default value is 256
+3. `--query` or `-q` sets the value of query number. Default value is 64
+
+#### Example usage:
+
+```Bash
+$ Release/Genie-and-Lamp-GPU -k 32 -d 128 -q 128
+$ Release/Genie-and-Lamp-GPU -q 256
+```
+
+#### Batch run
+
+Make sure you are in project directory, run
+
+```Bash
+[user@host Genie-and-Lamp-GPU] $ ruby runner.rb
+```
+
+You may add more test case by editing the arguments list in `runner.rb`:
+
+```Ruby
+def cases
+  [
+  #[topk, dimension, query]
+    [2,   8,         2],
+    [4,   16,        8],
+    [8,   32,        32],
+    [16,  64,        128],
+    [32,  64,        128],
+    [64,  128,       128],
+    [128, 128,       256],
+    [128, 256,       1028],
+  ]
+end
+```
+
+Here is some example output:
+
+```Bash
+==> running Release/Genie-and-Lamp-GPU -k 16 -d 64 -q 128
+TOPK = 16 DIMENSIONNUM = 64 QUERYNUM = 128
+GPU     : finished with total time : 0.83 with 26 iterations
+CPU_SCAN: the time of top-16 in CPU version is:0.35
+GPU_SCAN: GPU SCAN Time used: 0.0222176
+
+==> running Release/Genie-and-Lamp-GPU -k 32 -d 64 -q 128
+TOPK = 32 DIMENSIONNUM = 64 QUERYNUM = 128
+GPU     : finished with total time : 0.81 with 26 iterations
+CPU_SCAN: the time of top-32 in CPU version is:0.36
+GPU_SCAN: GPU SCAN Time used: 0.0217303
+
+==> running Release/Genie-and-Lamp-GPU -k 64 -d 128 -q 128
+TOPK = 64 DIMENSIONNUM = 128 QUERYNUM = 128
+GPU     : finished with total time : 1.02 with 31 iterations
+CPU_SCAN: the time of top-64 in CPU version is:0.68
+GPU_SCAN: GPU SCAN Time used: 0.0297324
+```