You have options for performing MATLAB calculations on the GPU:
You can transfer or create data on the GPU, and use the resulting gpuArray as input to enhanced built-in functions that support them. For more information and a list of functions that support gpuArray as inputs, see Run Built-In Functions on a GPU.
You can run your own MATLAB function of element-wise operations on a GPU.
Your decision on which solution to adopt depends on whether the functions you require are enhanced to support gpuArray, and the performance impact of transferring data to/from the GPU.
result = arrayfun(@myFunction,arg1,arg2);
Subsequent arguments provide inputs to the MATLAB function.
These input arguments can be workspace data or gpuArray. If any of
the input arguments is a gpuArray, the function executes on the GPU
and returns a gpuArray. (If none of the inputs is a gpuArray, then
bsxfun execute in the
In this example, a small function applies correction data to
an array of measurement data. The function defined in the file
function c = myCal(rawdata, gain, offst) c = (rawdata .* gain) + offst;
The function performs only element-wise operations when applying
a gain factor and offset to each element of the
Create some nominal measurement:
meas = ones(1000)*3; % 1000-by-1000 matrix
The function allows the gain and offset to be arrays of the
same size as
rawdata, so that unique corrections
can be applied to individual measurements. In a typical situation,
you might keep the correction data on the GPU so that you do not have
to transfer it for each application:
gn = rand(1000,'gpuArray')/100 + 0.995; offs = rand(1000,'gpuArray')/50 - 0.01;
Run your calibration function on the GPU:
corrected = arrayfun(@myCal,meas,gn,offs);
This runs on the GPU because the input arguments
offs are already in GPU memory.
Retrieve the corrected results from the GPU to the MATLAB workspace:
results = gather(corrected);
The function you pass into
bsxfun can contain the following built-in MATLAB functions
abs and acos acosh acot acoth acsc acsch asec asech asin asinh atan atan2 atanh beta betaln bitand bitcmp bitget bitor bitset bitshift bitxor ceil complex conj cos cosh cot coth csc csch
double eps eq erf erfc erfcinv erfcx erfinv exp expm1 false fix floor gamma gammaln ge gt hypot imag Inf int8 int16 int32 int64 intmax intmin isfinite isinf isnan ldivide le log log2
log10 log1p logical lt max min minus mod NaN ne not or pi plus pow2 power rand randi randn rdivide real reallog realmax realmin realpow realsqrt rem round sec sech sign sin single
sinh sqrt tan tanh times true uint8 uint16 uint32 uint64 xor + - .* ./ .\ .^ == ~= < <= > >= & | ~ && ||
|Scalar expansion versions of the following:|
* / \ ^
break continue else elseif for if return while
The function you pass to
bsxfun for execution on a GPU can contain the random number
randn. However, the GPU does not support the complete
functionality that MATLAB does.
bsxfun support the following functions for random matrix generation on
rand rand() rand('single') rand('double') randn randn() randn('single') randn('double')
randi randi() randi(IMAX, ...) randi([IMIN IMAX], ...) randi(..., 'single') randi(..., 'double') randi(..., 'int32') randi(..., 'uint32')
You do not specify the array size for random generation. Instead, the number of generated random values is determined by the sizes of the input variables to your function. In effect, there will be enough random number elements to satisfy the needs of any input or output variables.
For example, suppose your function
myfun.m contains the following code that includes generating and using the
function Y = myfun(X) R = rand(); Y = R.*X; end
If you use
arrayfun to run this function
with an input variable that is a gpuArray, the function runs on the
GPU, where the number of random elements for
determined by the size of
X, so you do not need
to specify it. The following code passes the gpuArray matrix
myfun on the GPU.
G = 2*ones(4,4,'gpuArray') H = arrayfun(@myfun, G)
G is a 4-by-4 gpuArray,
myfun generates 16 random value scalar elements for
R, one for each calculation with an element of
Random number generation by
bsxfun on the GPU uses the same global stream as gpuArray
random generation as described in Control the Random Stream for gpuArray. For more information about generating
random numbers on a GPU, and a comparison between GPU and CPU generation,
see Control Random Number Streams. For an example that shows performance comparisons for different
random generators, see Generating Random Numbers on a GPU.
The following limitations apply to the code within the function
bsxfun is evaluating
on a GPU.
arrayfun in MATLAB, matrix
exponential power, multiplication, and division (
\) perform element-wise calculations only.
Operations that change the size or shape of the input
or output arrays (
reshape, etc.), are not supported.
When generating random matrices with
randn, you do not
need to specify the matrix size, and each element of the matrix has
its own random stream. See Generate Random Numbers on a GPU.
bsxfun support read-only indexing (
subsref) and access
to variables of the parent (outer) function workspace from within
nested functions, i.e., those variables that exist in the function
on the GPU. Assignment or
subsasgn indexing of
these variables from within the nested function is not supported.
For an example of the supported usage see Stencil
Operations on a GPU
Anonymous functions do not have access to their parent function workspace.
Overloading the supported functions is not allowed.
The code cannot call scripts.
There is no
ans variable to hold
unassigned computation results. Make sure to explicitly assign to
variables the results of all calculations that you need to access.
The following language features are not supported:
persistent or global variables,
P-code files cannot contain a call to
bsxfun with gpuArray data.