Can we use memset( ) for non-zero initial value?

Accelerated Computing CUDA CUDA Programming and Performance
1

I want to initialize my variable array “test” with memset( ).

int test = NULL;
test = (int)malloc(sizeof(int) *ijmax);
memset(test, 0, sizeof(int) * 100 );

I get correct value when I use 0 as initial value, but I get some strange values when I set initial value to be non-zero values. For example, if I set it to 1,
memset(test, 1, sizeof(int) * 100 );

I will get test[0]=test[1]=…test[99]=16843009. Is there any body know what the problem is? Thanks,

Wangda

2

The memset() function writes bytes, not words. So writing 1 to sizeof(int)*100 bytes writes 00000001 to every set of 8-bits. Thus, each integer in binary looks like the following:-

0000 0001 0000 0001 0000 0001 0000 0001 (1 int = 4 bytes)

which in decimal is, exactly, 16843009.

I’m not sure what the best way to set desired values is. Maybe use memcpy or a small kernel to do it?

Anjul

3

Thank you very much, Anjul. :)