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Support real-time ML inference on the CPU
Discover how you can use BNNSGraph to accelerate the execution of your machine learning model on the CPU. We will show you how to use BNNSGraph to compile and execute a machine learning model on the CPU and share how it provides real-time guarantees such as no runtime memory allocation and single-threaded running for audio or signal processing models.
Chapters
- 0:00 - Introduction
- 1:18 - Introducing BNNS Graph
- 6:47 - Real-time processing
- 8:00 - Adopting BNNS Graph
- 14:52 - BNNS Graph in Swift
Resources
Related Videos
WWDC24
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0:01 - Create the graph
// Get the path to the mlmodelc. NSBundle *main = [NSBundle mainBundle]; NSString *mlmodelc_path = [main pathForResource:@"bitcrusher" ofType:@"mlmodelc"]; // Specify single-threaded execution. bnns_graph_compile_options_t options = BNNSGraphCompileOptionsMakeDefault(); BNNSGraphCompileOptionsSetTargetSingleThread(options, true); // Compile the BNNSGraph. bnns_graph_t graph = BNNSGraphCompileFromFile(mlmodelc_path.UTF8String, NULL, options); assert(graph.data); BNNSGraphCompileOptionsDestroy(options);
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0:02 - Create context and workspace
// Create the context. context = BNNSGraphContextMake(graph); assert(context.data); // Set the argument type. BNNSGraphContextSetArgumentType(context, BNNSGraphArgumentTypePointer); // Specify the dynamic shape. uint64_t shape[] = {mMaxFramesToRender, 1, 1}; bnns_graph_shape_t shapes[] = { (bnns_graph_shape_t) {.rank = 3, .shape = shape}, (bnns_graph_shape_t) {.rank = 3, .shape = shape} }; BNNSGraphContextSetDynamicShapes(context, NULL, 2, shapes); // Create the workspace. workspace_size = BNNSGraphContextGetWorkspaceSize(context, NULL) + NSPageSize(); workspace = (char *)aligned_alloc(NSPageSize(), workspace_size);
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0:03 - Calculate indices
// Calculate indices into the arguments array. dst_index = BNNSGraphGetArgumentPosition(graph, NULL, "dst"); src_index = BNNSGraphGetArgumentPosition(graph, NULL, "src"); resolution_index = BNNSGraphGetArgumentPosition(graph, NULL, "resolution"); saturationGain_index = BNNSGraphGetArgumentPosition(graph, NULL, "saturationGain"); dryWet_index = BNNSGraphGetArgumentPosition(graph, NULL, "dryWet");
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0:04 - Execute graph
// Set the size of the first dimension. BNNSGraphContextSetBatchSize(context, NULL, frameCount); // Specify the direct pointer to the output buffer. arguments[dst_index] = { .data_ptr = outputBuffers[channel], .data_ptr_size = frameCount * sizeof(outputBuffers[channel][0]) }; // Specify the direct pointer to the input buffer. arguments[src_index] = { .data_ptr = (float *)inputBuffers[channel], .data_ptr_size = frameCount * sizeof(inputBuffers[channel][0]) }; // Specify the direct pointer to the resolution scalar parameter. arguments[resolution_index] = { .data_ptr = &mResolution, .data_ptr_size = sizeof(float) }; // Specify the direct pointer to the saturation gain scalar parameter. arguments[saturationGain_index] = { .data_ptr = &mSaturationGain, .data_ptr_size = sizeof(float) }; // Specify the direct pointer to the mix scalar parameter. arguments[dryWet_index] = { .data_ptr = &mMix, .data_ptr_size = sizeof(float) }; // Execute the function. BNNSGraphContextExecute(context, NULL, 5, arguments, workspace_size, workspace);
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0:05 - Declare buffers
// Create source buffer that represents a pure sine wave. let srcChartData: UnsafeMutableBufferPointer<Float> = { let buffer = UnsafeMutableBufferPointer<Float>.allocate(capacity: sampleCount) for i in 0 ..< sampleCount { buffer[i] = sin(Float(i) / ( Float(sampleCount) / .pi) * 4) } return buffer }() // Create destination buffer. let dstChartData = UnsafeMutableBufferPointer<Float>.allocate(capacity: sampleCount) // Create scalar parameter buffer for resolution. let resolutionValue = UnsafeMutableBufferPointer<Float>.allocate(capacity: 1) // Create scalar parameter buffer for resolution. let saturationGainValue = UnsafeMutableBufferPointer<Float>.allocate(capacity: 1) // Create scalar parameter buffer for resolution. let mixValue = UnsafeMutableBufferPointer<Float>.allocate(capacity: 1)
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0:06 - Declare indices
// Declare BNNSGraph objects. let graph: bnns_graph_t let context: bnns_graph_context_t // Declare workspace. let workspace: UnsafeMutableRawBufferPointer // Create the indices into the arguments array. let dstIndex: Int let srcIndex: Int let resolutionIndex: Int let saturationGainIndex: Int let dryWetIndex: Int
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0:07 - Create graph and context
// Get the path to the mlmodelc. guard let fileName = Bundle.main.url( forResource: "bitcrusher", withExtension: "mlmodelc")?.path() else { fatalError("Unable to load model.") } // Compile the BNNSGraph. graph = BNNSGraphCompileFromFile(fileName, nil, BNNSGraphCompileOptionsMakeDefault()) // Create the context. context = BNNSGraphContextMake(graph) // Verify graph and context. guard graph.data != nil && context.data != nil else { fatalError()}
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0:08 - Finish initialization
// Set the argument type. BNNSGraphContextSetArgumentType(context, BNNSGraphArgumentTypePointer) // Set the size of the first dimension. BNNSGraphContextSetBatchSize(context, nil, UInt64(sampleCount)) // Create the workspace. workspace = .allocate(byteCount: BNNSGraphContextGetWorkspaceSize(context, nil), alignment: NSPageSize()) // Calculate indices into the arguments array. dstIndex = BNNSGraphGetArgumentPosition(graph, nil, "dst") srcIndex = BNNSGraphGetArgumentPosition(graph, nil, "src") resolutionIndex = BNNSGraphGetArgumentPosition(graph, nil, "resolution") saturationGainIndex = BNNSGraphGetArgumentPosition(graph, nil, "saturationGain") dryWetIndex = BNNSGraphGetArgumentPosition(graph, nil, "dryWet")
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0:09 - Create arguments array
// Copy slider values to scalar parameter buffers. resolutionValue.initialize(repeating: resolution.value) saturationGainValue.initialize(repeating: saturationGain.value) mixValue.initialize(repeating: mix.value) // Specify output and input arguments. var arguments = [(dstChartData, dstIndex), (srcChartData, srcIndex), (resolutionValue, resolutionIndex), (saturationGainValue, saturationGainIndex), (mixValue, dryWetIndex)] .sorted { a, b in a.1 < b.1 } .map { var argument = bnns_graph_argument_t() argument.data_ptr = UnsafeMutableRawPointer(mutating: $0.0.baseAddress!) argument.data_ptr_size = $0.0.count * MemoryLayout<Float>.stride return argument }
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0:10 - Execute graph
// Execute the function. BNNSGraphContextExecute(context, nil, arguments.count, &arguments,
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