FlatBuffers發佈時，順便也公佈了它的性能數據，具體數據請見Benchmark。
它的測試用例由以下數據構成"a set of about 10 objects containing an array, 4 strings, and a large variety of int/float scalar values of all sizes, meant to be representative of game data, e.g.
a scene format."
我感覺這樣測試如同兒戲，便自己設計了一個測試用例，主要關注CPU計算時間和內存空間佔用兩個指標，參考對象是protobuf。
測試用例爲：序列化一個通訊錄personal_info_list（table），通訊錄可以認爲是有每個人的信息(personal_info)的集合。每個人信息personal_info(table)有：個人id(uint)、名字(string)、年齡(byte)、性別(enum, byte)和電話號碼(ulong)。本來我想用struct表示personal_info(table)，但是struct不允許有數組或string成員，無奈我用table描述它了。相應的idl文件如下：
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namespace as.tellist;
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enum GENDER_TYPE : byte
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{
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MALE = 0,
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FEMALE = 1,
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OTHER = 2
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}
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table personal_info
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{
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id : uint;
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name : string;
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age : byte;
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gender : GENDER_TYPE;
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phone_num : ulong;
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}
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table personal_info_list
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{
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info : [personal_info];
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}
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root_type personal_info_list;
因爲要以protobuf做性能參考，列出protobuf的idl文件如下：
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package as.tellist;
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enum gender_type
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{
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MALE = 0;
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FEMALE = 1;
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OTHER = 2;
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}
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message personal_info
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{
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optional uint32 id = 1;
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optional string name = 2;
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optional uint32 age = 3;
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optional gender_type gender = 4;
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optional uint64 phone_num = 5;
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}
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message personal_info_list
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{
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repeated personal_info info = 1;
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}
若用C的struct描述對應的頭文件(其對應的程序稱之爲“二進制”)，如下：
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#ifndef __TELLIST_H__
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#define __TELLIST_H__
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enum
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{
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GENDER_TYPE_MALE = 0,
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GENDER_TYPE_FEMALE = 1,
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GENDER_TYPE_OTHER = 2,
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};
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inline const char **EnumNamesGENDER_TYPE()
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{
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static const char *names[] = { "MALE", "FEMALE", "OTHER"};
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return names;
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}
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inline const char *EnumNameGENDER_TYPE(int e)
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{
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return EnumNamesGENDER_TYPE()[e];
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}
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typedef struct personal_info_tag
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{
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unsigned id;
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unsigned char age;
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char gender;
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unsigned long long phone_num;
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char name[32];
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} personal_info;
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typedef struct personal_info_list_tag
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{
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int size;
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personal_info info[0];
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} personal_info_list;
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#endif
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測試時，在內存中構造37個personal_info對象，並序列化之，重複這個過程100萬次，然後再進行反序列化，再重複100萬次。
測試結果如下(補充：tellist_pb是protobuf測試程序，tellist_fb是FlatBuffers測試程序，tellist_fb是二進制測試程序，)：
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測試環境：12Core Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz
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free
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total used free shared buffers cached
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Mem: 66081944 62222028 3859916 0 196448 43690828
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-/+ buffers/cache: 18334752 47747192
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Swap: 975864 855380 120484
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protobuf三次測試結果：
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bin/tellist_pb
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encode: loop = 1000000, time diff = 14210ms
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decode: loop = 1000000, time diff = 11185ms
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buf size:841
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bin/tellist_pb
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encode: loop = 1000000, time diff = 14100ms
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decode: loop = 1000000, time diff = 11234ms
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buf size:841
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bin/tellist_pb
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encode: loop = 1000000, time diff = 14145ms
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decode: loop = 1000000, time diff = 11237ms
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buf size:841
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序列化後佔用內存空間841Byte，encode平均運算時間42455ms / 3 = 14151.7ms，decode平均計算時間33656ms / 3 = 11218.7ms
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flatbuffers三次測試結果：
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bin/tellist_fb
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encode: loop = 1000000, time diff = 11666ms
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decode: loop = 1000000, time diff = 1141ms
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buf size:1712
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bin/tellist_fb
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encode: loop = 1000000, time diff = 11539ms
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decode: loop = 1000000, time diff = 1200ms
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buf size:1712
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bin/tellist_fb
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encode: loop = 1000000, time diff = 11737ms
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decode: loop = 1000000, time diff = 1141ms
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buf size:1712
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序列化後佔用內存空間1712Byte，encode平均運算時間34942ms / 3 = 11647.3ms，decode平均計算時間3482ms / 3 = 1160.7ms
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二進制三次測試結果：
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bin/tellist
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encode: loop = 1000000, time diff = 4967ms
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decode: loop = 1000000, time diff = 688ms
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buf size:304
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bin/tellist
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encode: loop = 1000000, time diff = 4971ms
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decode: loop = 1000000, time diff = 687ms
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buf size:304
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bin/tellist
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encode: loop = 1000000, time diff = 4966ms
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decode: loop = 1000000, time diff = 686ms
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buf size:304
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序列化後佔用內存空間304Byte，encode平均運算時間14904ms / 3 = 4968ms，decode平均計算時間2061ms / 3 = 687ms
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測試環境：1 Core Intel(R) Core(TM) i5-3210M CPU @ 2.50GHz
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free
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total used free shared buffers cached
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Mem: 753932 356036 397896 0 50484 224848
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-/+ buffers/cache: 80704 673228
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Swap: 1324028 344 1323684
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protobuf三次測試結果：
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./bin/tellist_pb
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encode: loop = 1000000, time diff = 12451ms
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decode: loop = 1000000, time diff = 9662ms
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buf size:841
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./bin/tellist_pb
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encode: loop = 1000000, time diff = 12545ms
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decode: loop = 1000000, time diff = 9840ms
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buf size:841
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./bin/tellist_pb
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encode: loop = 1000000, time diff = 12554ms
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decode: loop = 1000000, time diff = 10460ms
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buf size:841
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序列化後佔用內存空間841Byte，encode平均運算時間37550ms / 3 = 12516.7ms，decode平均計算時間29962ms / 3 = 9987.3ms
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flatbuffers三次測試結果：
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bin/tellist_fb
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encode: loop = 1000000, time diff = 9640ms
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decode: loop = 1000000, time diff = 1164ms
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buf size:1712
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bin/tellist_fb
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encode: loop = 1000000, time diff = 9595ms
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decode: loop = 1000000, time diff = 1170ms
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buf size:1712
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bin/tellist_fb
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encode: loop = 1000000, time diff = 9570ms
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decode: loop = 1000000, time diff = 1172ms
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buf size:1712
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序列化後佔用內存空間1712Byte，encode平均運算時間28805ms / 3 = 9345ms，decode平均計算時間3506ms / 3 = 1168.7ms
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二進制三次測試結果：
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bin/tellist
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encode: loop = 1000000, time diff = 4194ms
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decode: loop = 1000000, time diff = 538ms
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buf size:304
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bin/tellist
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encode: loop = 1000000, time diff = 4387ms
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decode: loop = 1000000, time diff = 544ms
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buf size:304
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bin/tellist
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encode: loop = 1000000, time diff = 4181ms
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decode: loop = 1000000, time diff = 533ms
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buf size:304
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序列化後佔用內存空間304Byte，encode平均運算時間12762ms / 3 = 4254ms，decode平均計算時間1615ms / 3 = 538.3ms
上面的二進制程序的結果無論在內存空間佔用還是cpu計算時間這兩個指標上都是最快的。但本文只討論FlatBuffers和protobuf，所以不讓它的結果參與比較。
從以上數據看出，在內存空間佔用這個指標上，FlatBuffers佔用的內存空間比protobuf多了兩倍。序列化時二者的cpu計算時間FB比PB快了3000ms左右，反序列化時二者的cpu計算時間FB比PB快了9000ms左右。FB在計算時間上佔優勢，而PB則在內存空間上佔優（相比FB，這也正是它計算時間比較慢的原因）。
上面的測試環境是在公司的linux server端和我自己的mac pro分別進行的。請手機端開發者自己也在手機端進行下測試， 應該能得到類似的結果。Google宣稱FB適合遊戲開發是有道理的，如果在乎計算時間我想它也適用於後臺開發。
另外，FB大量使用了C++11的語法，其從idl生成的代碼接口不如protubuf友好。不過相比使用protobuf時的一堆頭文件和佔18M之多的lib庫，FlatBuffers僅僅一個"flatbuffers/flatbuffers.h"就足夠了。
測試程序已經上傳到百度網盤，點擊這個鏈接即可下載。歡迎各位的批評意見。
