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I am wondering why Xcode uses CPU for Metal GPU shader program execution for Swift. With Objective-C Metal, it finishes instantly. But the same shader program, when called from Swift, takes many seconds. GPU is idle while CPU runs 99%. I use the following line to choose GPU in Swift. But doesn't seem to choose real GPU. let device: MTLDevice = MTLCreateSystemDefaultDevice()! For Objective-C, I use the same default device. This chooses GPU correctly. MTLDevice device = MTLCreateSystemDefaultDevice(); Is there any way I can choose GPU in Swift Metal?

I have a following MTLBuffer created. How can I send INPUTVALUE to the memINPUT buffer? I need to send repeatedly in Objective-C. // header file @property id<MTLBuffer> memINPUT; // main file int length = 1000; ... memINPUT = [_device newBufferWithLength:(sizeof(float)*length) options:0]; ... float INPUTVALUE[length]; for (int i=0; i < length; i++) { INPUTVALUE[i] = (float)i; } // How to send to INPUTVALUE to memINPUT? ... The following is Swift version. I am looking for Objective-c version. memINPUT.contents().copyMemory(from: INPUTVALUE, byteCount: length * MemoryLayout<Float>.stride);

I am new to Metal. I need to port OpenCL compute shader programs to Metal compute shaders. I am having trouble in finding sample codes in Metal and Swift, Objective-C. I can see examples with GPU buffer objects only. As in the following OpenCL shader function, I need to pass uniform constant float and integer values along with GPU buffer pointers. I only use compute shaders. __kernel void testfunction ( float ratio1, int opr1, int opr2, __global float *INPUT1, __global float *INPUT2, __global float *OUTPUT } { int peIndex = get_global_id(0); // main compute block } How can I code these in Metal? And how can I set/pass these parameter values in Swift and Objective-c main programs?