Archive for the ‘GPGPU’ Category

Coalescing Memory

July 1, 2008

Coalescing as per the dictionary means uniting. One of the best things about computer science terminology is they are at most of the times based on the dictionary meaning. (Yup … as always there are exceptions ,,like “Transperent”)

In GPGPU NVIDIA

What does Coaelscing actually mean  ?  I found the following answer good

Coalescing means that a memory read by consecutive threads in a warp is combined by the hardware into several, wide memory reads. The requirement is that the threads in the warp must be reading memory in order. For example, if you have a float array called data[] and you want to read many floats starting at offset n, then thread 0 in the warp must read data[n], thread 1 must read data[n+1], and so on. Those 32-bit reads, which are issued simultaneously, are merged into several 384 bit reads in order to efficiently use the memory bus. Coalescing is a warp-level activity, not a thread-level activity.