Question about bank conflict Chapter 5.1.2.4 of Cuda Prog. Guide

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi,
I don’t quite understand about the bank conflict as outlined on the page 57 of Cuda Programming Guide. It does not have conflict if the structure contains three floats, but have conflict if the structure contains two float.

If the structure has three floats, then :
Thread 0 - Bank 0 (0.x), Bank 1 (0.y), Bank 2(0.z)
Thread 1 - Bank 3 (1.x), Bank 4 (1.y), Bank 5(1.z)
Thread 2 - Bank 6 (2.x), Bank 7 (2.y), Bank 8(2.z)
.
.
But for Thread 6, it will wrap around and it will access Bank 1, 2, and 3 which are already accessed by Thread 0 and Thread 1. So, there should be bank conflict…

Can anybody please explain this ? Thanks.

2

Threads only access one 32-bit word simultaneously. Thus, there could only be a bank conflict down any individual column of your table.

3

Hi,
Just say, there are two structs :

struct type1 { float x, y, z}

or

struct type2 { float x, y}

So, how does Cuda store the struct in the bank ?