使用profile來得到程序運行信息 profile程序可以用來監測程序不同部分（主要是各個函數）的使用時間和調用次數。 因此可以使用這個程序來鑒別程序中那個函數是整個程序的瓶頸，從而可以通過優化這個 函數來提高程序的性能。 Unix/Linux系統提供了GPROF這個profile程序。該程序提供兩種信息： 1、程序中每個函數的CPU使用時間。 2、每個函數的調用次數。並提供簡單調用關系圖。 使用GPROF步驟如下： 1、用gcc或g++編譯程序時，使用-pg參數，如：g++ -pg -o test.out test.cpp 2、執行編譯得到的運行程序。如：./test.out 該步驟運行程序的時間會稍慢於正常編譯出來的程序執行時間。而且會產生一個 gmon.out文件。 3、使用gprof命令。如：gprof test.out 於是可以在顯示器上看到上述信息。 ///////////////////////////////////////////////////////////////////////////// ps1：test.cpp程序使用gprof得到的結果 Flat profile: Each sample counts as 0.01 seconds. % cumulative self self total time seconds seconds calls ms/call ms/call name 60.00 0.09 0.09 50 1.80 1.80 test2(int) 40.00 0.15 0.06 50 1.20 1.20 test1(int) % the percentage of the total running time of the time program used by this function. cumulative a running sum of the number of seconds accounted seconds for by this function and those listed above it. self the number of seconds accounted for by this seconds function alone. This is the major sort for this listing. calls the number of times this function was invoked, if this function is profiled, else blank. self the average number of milliseconds spent in this ms/call function per call, if this function is profiled, else blank. total the average number of milliseconds spent in this ms/call function and its descendents per call, if this function is profiled, else blank. name the name of the function. This is the minor sort for this listing. The index shows the location of the function in the gprof listing. If the index is in parenthesis it shows where it would appear in the gprof listing if it were to be printed. Call graph (eXPlanation follows) granularity: each sample hit covers 4 byte(s) for 6.67% of 0.15 seconds index % time self children called name <spontaneous> [1] 100.0 0.00 0.15 main [1] 0.09 0.00 50/50 test2(int) [2] 0.06 0.00 50/50 test1(int) [3] ----------------------------------------------- 0.09 0.00 50/50 main [1] [2] 60.0 0.09 0.00 50 test2(int) [2] ----------------------------------------------- 0.06 0.00 50/50 main [1] [3] 40.0 0.06 0.00 50 test1(int) [3] ----------------------------------------------- This table describes the call tree of the program, and was sorted by the total amount of time spent in each function and its children. Each entry in this table consists of several lines. The line with the index number at the left hand margin lists the current function. The lines above it list the functions that called this function, and the lines below it list the functions this one called. This line lists: index A unique number given to each element of the table. Index numbers are sorted numerically. The index number is printed next to every function name so it is easier to look up where the function in the table. % time This is the percentage of the `total' time that was spent in this function and its children. Note that due to different viewpoints, functions excluded by options, etc, these numbers will NOT add up to 100%. self This is the total amount of time spent in this function. children This is the total amount of time propagated into this function by its children. called This is the number of times the function was called. If the function called itself recursively, the number only includes non-recursive calls, and is followed by a `+' and the number of recursive calls. name The name of the current function. The index number is printed after it. If the function is a member of a cycle, the cycle number is printed between the function's name and the index number. For the function's parents, the fields have the following meanings: self This is the amount of time that was propagated directly from the function into this parent. children This is the amount of time that was propagated from the function's children into this parent. called This is the number of times this parent called the function `/' the total number of times the function was called. Recursive calls to the function are not included in the number after the `/'. name This is the name of the parent. The parent's index number is printed after it. If the parent is a member of a cycle, the cycle number is printed between the name and the index number. If the parents of the function cannot be determined, the Word `<spontaneous>' is printed in the `name' field, and all the other fields are blank. For the function's children, the fields have the following meanings: self This is the amount of time that was propagated directly from the child into the function. children This is the amount of time that was propagated from the child's children to the function. called This is the number of times the function called this child `/' the total number of times the child was called. Recursive calls by the child are not listed in the number after the `/'. name This is the name of the child. The child's index number is printed after it. If the child is a member of a cycle, the cycle number is printed between the name and the index number. If there are any cycles （circles） in the call graph， there is an entry for the cycle-as-a-whole. This entry shows who called thecycle （as parents） and the members of the cycle （as children.）The `+' recursive calls entry shows the number of function calls thatwere internal to the cycle， and the calls entry for each member shows，for that member， how many times it was called from other members ofthe cycle. Index by function name [3]
