To optimize generated code that copies consecutive array elements,
the code generator tries to replace the code with a memcpy call.
A memcpy call can be more efficient than code,
such as a for-loop or multiple, consecutive element
assignments.
| Code Generated with the memcpy Optimization | Code Generated without the memcpy Optimization |
|---|---|
memcpy(&C[0], &A[0], 10000U * sizeof(double)); | for (i0 = 0; i0 < 10000; i0++) {
C[i0] = A[i0]; |
memcpy(&Z[0], &X[0],1000U * sizeof(double)); | Z[0] = X[0]; Z[1] = X[1]; Z[2] = X[2]; ... Z[999] = X[999]; |
The code generator invokes the memcpy optimization
if the following conditions are true:
The memcpy optimization is enabled.
The number of bytes to copy is greater than or equal
to the memcpy threshold. The number of bytes
to copy is the number of array elements multiplied by the number of
bytes required for the C/C++ data type.
To enable or disable the memcpy optimization:
At the command line, set the code configuration object
property EnableMemcpy to true or false,
respectively. The default value is true.
In the MATLAB® Coder™ app, set Use memcpy
for vector assignment to Yes or No respectively.
The default value is Yes.
The default memcpy threshold is
64 bytes. To change the threshold:
At the command line, set the code configuration object
property MemcpyThreshold.
In the MATLAB Coder app, set Memcpy threshold (bytes).
The memset optimization also uses
the memcpy threshold.