Arrays filled with garbage after copying to device Should I use cudaMemcpyToArray?

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi there,

I’m having trouble copying data to the device.

I have a small test program that I’m trying to port in order

to run on a GPU. Half of the program generates a random

data file ([font=“Courier New”]400MB[/font]) with a pattern inserted often.

The reader-half of the program, reads through the data

file and uses [font=“Courier New”]memcmp[/font] to search for the pattern in each

page it reads in.

I copied the [font=“Courier New”]memcmp[/font] routine (and properly attributed it)

so that it is a [font=“Courier New”]device[/font] routine, under a different name.

I read in a page (4096 bytes) into an appropriately sized

array and attempt to copy it over. Each page has 32 records,

sized 128 bytes each.

#define TARGET_PATTERN "kevin"

...

bytes_read = fread( h_page_buffer, 1, parameters->page_size, input_file);

...

char* d_page_buffer;

char h_pattern[] = TARGET_PATTERN;

char* d_pattern;

cudaMalloc( &d_page_buffer, buf_sz );

cudaMalloc( &d_pattern, strlen(TARGET_PATTERN) * sizeof(char) );

cudaMemcpy( d_page_buffer, h_page_buffer, buf_sz, cudaMemcpyHostToDevice );

cudaMemcpy( d_pattern, h_pattern, strlen(TARGET_PATTERN) * sizeof(char), cudaMemcpyHostToDevice );

compare<<< 1, num_records_per_page >>>( d_page_buffer, ... , d_pattern );

I have a shared variable that’s used to track how many

matches have been found, but the count is zero.

Stepping through, using [font=“Courier New”]cuda-gdb[/font], I see

compare (__cuda_0=0x100100 "(", __cuda_1=0x100000, __cuda_2=128, __cuda_3=5, __cuda_4=0x100200 "?

compare (__cuda_0=0x100100 “(”, __cuda_1=0x100000, __cuda_2=128, __cuda_3=5, __cuda_4=0x100200 “?\001\020”)

01

compare (__cuda_0=0x100100 “(”, __cuda_1=0x100000, __cuda_2=128, __cuda_3=5, __cuda_4=0x100200 “?\001\020”)

20")

which confuses me, beyond showing me that I’m doing

something incorrectly.

At the minimum, I expected the value of [font=“Courier New”]__cuda_4[/font] to be

[font=“Courier New”]“kevin”[/font], not [font=“Courier New”]“?\001\020”[/font].

[font=“Courier New”]__cuda_0[/font] also appears incorrect. Using a hex editor, I can

see that the first record’s ASCII representation is (ignore

line breaks)

kom"XV*t']nKVXU5cKB&AUSeR]Gtd=u4Huf5-7_I?$; _MZ9n[]m\^N":0|[2LUZ-;/h2c@Yq}Sx'2wI_Ta97_3*]@(%_^.TDmj&{?S0YFis\lk_Q+_P6i*6_I?kevin

I’m not sure why[font=“Courier New”] __cuda_0[/font]'s value is a single character, [font=“Courier New”]“)”[/font].

I believe these are the reasons I can’t find a match.

Could anyone help point out any errors or help with guidance?

Am I missing something regarding preserving values or not

copying them properly?

Thanks in advance.