The low speedup of written CUDA code -


i written 2 separate code same program in cpu (c++) , cuda. don't know why speedup of cuda code less cpu code.
have 3 matrices h, e, f , operations performed on these. speedup time in cpu code 0.004s , in cuda code is: 0.006s dimensions of matrices 32*32. in kernel code defined 3 shared memory variables matrix_h, matrix_e, matrix_fand copied dev_h, dev_e, dev_f values global memory shared memory speedup access time of memory , copied calculated shared memory variables global memory.
it's because of lot of parameters in kernel call or elsewhere? 

__global__ void kernel_scorematrix(char *dev_seqa, char *dev_seqb,     int *dev_h, int *dev_e, int *dev_f, int *dev_i_side, int *dev_j_side,    int *dev_lena, int *dev_idx_array, int *dev_array_length) {    __shared__ int matrix_h[1024];    __shared__ int matrix_e[1024];    __shared__ int matrix_f[1024];     int x= threadidx.x;    int y= threadidx.y;     //calculate current_cell execute threads    int current_cell = *(dev_lena)*(y) + x;     matrix_h[current_cell]=dev_h[current_cell];    matrix_e[current_cell]=dev_e[current_cell];    matrix_f[current_cell]=dev_f[current_cell];     int index=0;     int scorematrix[4];     //for determine cells  must compute in time    (int i=0; i<*(dev_array_length); i++)     if (current_cell== dev_idx_array[i]){             scorematrix[0] = h_matrix(current_cell, x, y, matrix_h, dev_seqa, dev_seqb, dev_lena);              scorematrix[1] = e_matrix(current_cell, matrix_e, matrix_h, dev_lena);             scorematrix[2] = f_matrix(current_cell, matrix_f, matrix_h, dev_lena);             scorematrix[3] = 0;             dev_h[current_cell] = findmax(scorematrix,4, index); }

in main function:

dim3 threadsperblock(32, 32); kernel_scorematrix<<<1,threadsperblock>>>(dev_seqa, dev_seqb, dev_h, dev_e, dev_f,          dev_i_side, dev_j_side, dev_lena, dev_idx_array, dev_array_length);

a threadblock by definition executes on single sm. regardless of how many threads threadblock contains, only execution resources have available execution of particular threadblock resources in (single) sm. since nvidia gpus contain more single sm, in order keep gpu busy (which necessary most performance), it's necessary launch grids more 1 threadblock. reasonable rule of thumb have @ least 2-4x number of threadblocks have sms, , there little harm in having lot more threadblocks that.

but if launch kernel 1 threadblock, limited 1 sm. , therefore getting approximately 1/(number of sms in gpu) of performance available machine. number of threads in threadblock not affect factor.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

node.js - Getting the socket id,user id pair of a logged in user(s) -

i have web application done using node js , in it,i have authentication system requires users log in before can access pages. have 2 pages,the homepage , updates page. from read docs,a new socket id issued when user opens tab in browser. me being admin,i know socket id of logged in user , more so,the socket id,logged in user id pair logged in users. what method can use socket id,logged in user id pair make sure broadcast realtime info users online?.
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua
Read more