# RamDrive with video card ram

9

I use the R language for heavy matrix calculations. I'm using gpu for performance gain, which is fantastic indeed.

However, I would like to take another step and dump the 2gb matrix of data directly into the ram of the video card

Or maybe, create a ramdrive with the ram of the video card which is ddr5

Would that be possible?

asked by anonymous 03.04.2015 / 01:40

2

Yes, there is this possibility in R, since parallel computing comes from the beginnings in R, just take a look at the High-Performance and Parallel Computing with R section in CRAN, such as link to streamline.

Yes, you can write in C and call in R if you prefer, like this example:

``````#include
#include <cufft.h>
/* This function is written for R to compute 1D FFT.
n - [IN] the number of complex we want to compute
inverse - [IN] set to 1 if use inverse mode
h_idata_re - [IN] input data from host (R, real part)
h_idata_im - [IN] input data from host (R, imaginary part)
h_odata_re - [OUT] results (real) allocated by caller
h_odata_im - [OUT] results (imaginary) allocated by caller
*/
extern "C"
void cufft(int *n, int *inverse, double *h_idata_re,
double *h_idata_im, double *h_odata_re, double *h_odata_im)
{
cufftHandle plan;
cufftDoubleComplex *d_data, *h_data;
cudaMalloc((void**)&d_data, sizeof(cufftDoubleComplex)*(*n));
h_data = (cufftDoubleComplex *) malloc(sizeof(cufftDoubleComplex) * (*n));

// Convert data to cufftDoubleComplex type
for(int i=0; i< *n; i++) {
h_data[i].x = h_idata_re[i];
h_data[i].y = h_idata_im[i];
}

cudaMemcpy(d_data, h_data, sizeof(cufftDoubleComplex) * (*n),
cudaMemcpyHostToDevice);
// Use the CUFFT plan to transform the signal in place.
cufftPlan1d(&plan, *n, CUFFT_Z2Z, 1);
if (!*inverse ) {
cufftExecZ2Z(plan, d_data, d_data, CUFFT_FORWARD);
} else {
cufftExecZ2Z(plan, d_data, d_data, CUFFT_INVERSE);
}

cudaMemcpy(h_data, d_data, sizeof(cufftDoubleComplex) * (*n),
cudaMemcpyDeviceToHost);
// split cufftDoubleComplex to double array
for(int i=0; i<*n; i++) {
h_odata_re[i] = h_data[i].x;
h_odata_im[i] = h_data[i].y;
}

// Destroy the CUFFT plan and free memory.
cufftDestroy(plan);
cudaFree(d_data);
free(h_data);
}
``````

After doing wrapper in R:

``````cufft1D <- function(x, inverse=FALSE)
{
}
n <- length(x)
rst <- .C("cufft",
as.integer(n),
as.integer(inverse),
as.double(Re(z)),
as.double(Im(z)),
re=double(length=n),
im=double(length=n))
rst <- complex(real = rst[["re"]], imaginary = rst[["im"]])
return(rst)
}
``````

It's not so simple, there are some settings and some issues related to libraries, but that up there is just to get an idea. Here in this link has a nice tutorial and tb is the source from which I took the functions.

p.s .: a 2 GB array is not so large and heavy so if you use the right shapes in your algorithm.

18.07.2015 / 02:27