CUDA Programming Concepts Quiz

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Questions and Answers

What is the primary purpose of using shared memory in CUDA programming?

  • To reduce the overall memory requirement of the program.
  • To increase the complexity of kernel execution.
  • To optimize the reuse of global memory data. (correct)
  • To enhance data transfer rates to the CPU.

What is the focus of the concept of 'Tiled Multiply' in CUDA?

  • Dividing computations into manageable blocks. (correct)
  • Minimizing power consumption during kernel execution.
  • Implementing multi-threaded CPU processes.
  • Storing large arrays on the device.

Which component is crucial for synchronization in CUDA runtime?

  • The global memory allocator.
  • The host memory controller.
  • The synchronization function. (correct)
  • The graphics processing unit (GPU) power manager.

In G80 architecture, what is a significant consideration for managing memory size?

<p>Balancing registers and shared memory usage. (D)</p> Signup and view all the answers

What does tiling size impact in matrix multiplication kernels?

<p>The execution time and resource utilization. (A)</p> Signup and view all the answers

What is a key advantage of OpenACC?

<p>It uses a simple directive-based model for parallel computing. (A)</p> Signup and view all the answers

What does the 'kernels' directive in OpenACC indicate?

<p>To parallelize the execution of specific code blocks. (B)</p> Signup and view all the answers

What is a significant difference between OpenACC and CUDA?

<p>OpenACC uses high-level directives while CUDA is a low-level programming model. (A)</p> Signup and view all the answers

What is the purpose of the 'loop' directive in OpenACC?

<p>To indicate that loop iterations can run in parallel. (C)</p> Signup and view all the answers

How does OpenACC support single code for multiple platforms?

<p>By providing directives that are interpreted by compilers for different architectures. (C)</p> Signup and view all the answers

What is a key advantage of multicore architecture?

<p>Enhanced energy efficiency during multitasking (B)</p> Signup and view all the answers

Which of the following statements about OpenACC parallel directive is accurate?

<p>It allows for explicit data management for improved performance. (C)</p> Signup and view all the answers

Which of the following best describes MIMD architecture?

<p>Each processor can execute its own instruction independently (A)</p> Signup and view all the answers

What role does the 'restrict' keyword play in C with OpenACC?

<p>It indicates that pointers do not alias during execution. (C)</p> Signup and view all the answers

What differentiates heterogeneous multicore processors from homogeneous multicore processors?

<p>Heterogeneous multicore processors consist of cores with varied capabilities (A)</p> Signup and view all the answers

What is the primary focus of the OpenACC model?

<p>Abstracting parallel programming through high-level directives. (A)</p> Signup and view all the answers

Flynn's Taxonomy categorizes computer architectures. Which category does SIMD belong to?

<p>Single Instruction Multiple Data (B)</p> Signup and view all the answers

Which of the following is a common disadvantage of multicore processors?

<p>Greater software complexity for utilizing all cores (A)</p> Signup and view all the answers

What is the primary focus of throughput-oriented architecture?

<p>Enhancing the overall system's capacity to handle tasks (A)</p> Signup and view all the answers

Which architecture allows for parallel processing of different instructions?

<p>MIMD (C)</p> Signup and view all the answers

How do processor interconnects generally affect multicore systems?

<p>They impact the data transfer rates between cores (D)</p> Signup and view all the answers

What is a defining characteristic of SISD architecture?

<p>Single instruction executed on a single data stream (A)</p> Signup and view all the answers

Which of the following best explains the relationship of cores in homogeneous multicore processors?

<p>Cores are interchangeable and identical (A)</p> Signup and view all the answers

What is the purpose of the Master/Worker pattern in programming?

<p>To distribute tasks and manage threads (B)</p> Signup and view all the answers

Which of the following best describes the Fork/Join pattern?

<p>It divides a task into subtasks that can be executed in parallel. (C)</p> Signup and view all the answers

How does the Map-Reduce programming model function?

<p>It splits large datasets into smaller subsets, processes them, and combines the outputs. (A)</p> Signup and view all the answers

What does the term 'Partitioning' refer to in algorithm structure?

<p>Dividing data into smaller segments for parallel processing. (C)</p> Signup and view all the answers

What is a key benefit of using the Single Program Multiple Data (SPMD) model?

<p>It allows different computations on each data element. (A)</p> Signup and view all the answers

Which statement accurately describes Bitonic sorting?

<p>It can sort data in both ascending and descending order only after constructing a bitonic sequence. (B)</p> Signup and view all the answers

What are compiler directives used for?

<p>To instruct the compiler on how to process specific pieces of code. (D)</p> Signup and view all the answers

What is the primary function of 'communication' in a parallel programming context?

<p>To transfer data between processes or threads to ensure synchronization. (B)</p> Signup and view all the answers

In the context of parallel programming, what does 'Agglomeration' refer to?

<p>Combining multiple smaller tasks into fewer, larger tasks for improved efficiency. (D)</p> Signup and view all the answers

What is the primary focus of loop parallelism?

<p>To execute iterations of a loop simultaneously across multiple threads. (A)</p> Signup and view all the answers

Which statement best describes the difference between Thrust and CUDA?

<p>Thrust provides a higher-level interface, while CUDA offers low-level control. (C)</p> Signup and view all the answers

Which of the following examples illustrates a practical application of Thrust?

<p>Sorting an array of numbers efficiently (B)</p> Signup and view all the answers

What is the main purpose of the PCAM example in parallel computing?

<p>To showcase parallel computation and data handling techniques. (B)</p> Signup and view all the answers

Which characteristic defines a Bitonic Set?

<p>It consists of two sequentially increasing and then decreasing subsequences. (D)</p> Signup and view all the answers

What is the purpose of barriers in OpenCL?

<p>To control the execution order within a single queue. (C)</p> Signup and view all the answers

Which of the following describes the role of kernel arguments in OpenCL?

<p>They define the input and/or output data that the kernel can access. (A)</p> Signup and view all the answers

What is one of the main advantages of using local memory in an OpenCL program?

<p>It reduces the bandwidth needed for global memory access. (B)</p> Signup and view all the answers

What type of decomposition does Amdahl’s Law pertain to in parallel programming?

<p>Task Decomposition (C)</p> Signup and view all the answers

In OpenCL, what does the term 'granularity' refer to?

<p>The size of data chunks being processed. (C)</p> Signup and view all the answers

Which method can significantly improve performance in OpenCL matrix multiplication?

<p>Reducing work-item overhead by assigning one row of C per work-item. (D)</p> Signup and view all the answers

What is the PCAM methodology associated with in parallel programming?

<p>Task decomposition approaches. (D)</p> Signup and view all the answers

What kind of data would you typically use vector operations for in OpenCL?

<p>Batch processing of multiple values. (A)</p> Signup and view all the answers

What is the first step in creating a parallel program, as outlined in the common steps?

<p>Identify potential concurrency in the program. (C)</p> Signup and view all the answers

How does the orchestration and mapping aspect influence parallel programming?

<p>It maps logical tasks to physical processing elements. (D)</p> Signup and view all the answers

Which programming element defines the structure of kernel operations in OpenCL?

<p>Kernel Objects (B)</p> Signup and view all the answers

What is the effect of using pipe decomposition in parallel programming?

<p>Increases data throughput between tasks. (D)</p> Signup and view all the answers

What does the term 'profiling' refer to in the context of OpenCL?

<p>Measuring performance characteristics of kernels. (B)</p> Signup and view all the answers

What is a primary outcome of optimizing an OpenCL program for performance?

<p>Enhanced utilization of parallel processing resources. (C)</p> Signup and view all the answers

What is the primary difference between scalar and SIMD code?

<p>SIMD code allows parallel processing of multiple data elements. (C)</p> Signup and view all the answers

Which type of architecture uses shared memory for multicore programming?

<p>Shared memory architecture. (C)</p> Signup and view all the answers

What is Amdahl's Law primarily concerned with?

<p>Predicting the speedup in a task when using parallel processing. (A)</p> Signup and view all the answers

In the context of multicore programming, what does granularity refer to?

<p>The size of each task in relation to the data being processed. (B)</p> Signup and view all the answers

What feature characterizes OpenMP in parallel programming?

<p>It provides support through directives for code parallelization. (C)</p> Signup and view all the answers

What is the role of mutual exclusion in parallel programming?

<p>To prevent multiple processes from accessing shared resources simultaneously. (D)</p> Signup and view all the answers

Which of the following describes message passing in distributed memory processors?

<p>Processes work independently and exchange information via messages. (C)</p> Signup and view all the answers

What does performance analysis in multicore programming involve?

<p>Evaluating the efficiency of the code in terms of speed and resource utilization. (B)</p> Signup and view all the answers

Which programming model is characterized by dynamic multithreading?

<p>Thread creation based on runtime demands. (C)</p> Signup and view all the answers

What advantage does Cilk's work-stealing scheduler provide?

<p>It optimizes load balancing among processors. (A)</p> Signup and view all the answers

Which of the following is a characteristic of distributed memory multicore architecture?

<p>Each processor has its local memory, requiring explicit communication. (A)</p> Signup and view all the answers

What does the term 'coverage' refer to in the context of parallelism?

<p>The extent to which a parallel program can utilize available processors. (D)</p> Signup and view all the answers

What is a common limitation of SIMD operations?

<p>They are not suitable for all types of algorithms. (B)</p> Signup and view all the answers

Flashcards

Shared Memory

A type of memory accessible by multiple threads in a parallel computing architecture.

Tiled Multiply

A technique for optimizing matrix multiplication by dividing the matrix into smaller tiles.

Device Runtime Component (Synchronization)

A part of a computing system that coordinates the execution of tasks on a device.

First-Order Size Considerations

Factors that influence performance based on the size of computations and data.

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CUDA Kernel Execution Configuration

Setting properties for CUDA kernels, such as the number of threads or blocks.

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Multicore Architecture

A computer architecture with multiple independent processing units (cores) on a single chip.

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SISD

Single Instruction, Single Data. A computer architecture where a single instruction is executed on a single piece of data.

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SIMD

Single Instruction, Multiple Data. A computer architecture where a single instruction is executed on multiple pieces of data.

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MIMD

Multiple Instructions, Multiple Data. A computer architecture where multiple instructions are executed on multiple pieces of data.

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Flynn's Taxonomy

A classification of computer architectures based on the number of instructions and data streams.

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Homogeneous Multicore

A multicore processor with identical cores.

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Heterogeneous Multicore

A multicore processor with different types of cores.

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Multi-core processor

A central processing unit (CPU) with multiple independent processing units (cores) on a single integrated circuit.

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Advantages of Multicore

Faster processing speed and enhanced performance due to parallel execution of tasks.

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Disadvantages of Multicore

Increased complexity in programming, needing specific programming techniques to take advantage of them.

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Scalar operation

A single-data operation. Each data element is processed one at a time.

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Shared Memory Multicore

A multicore architecture where all cores share the same main memory. Data is accessible by all cores.

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Distributed Memory Multicore

A multicore architecture where each core has its own separate memory. Data must be moved between cores explicitly.

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Multicore Programming

Writing programs that can take advantage of multiple cores in a processor. Doing calculations on multiple processors simultaneously.

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OpenMP

An application programming interface (API) model that supports multi-platform shared memory parallelism in C, C++, and Fortran. Programming model that assists parallel programming.

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Dynamic Multithreading

A way to manage threads that aren't bound to a specific core, often used in parallel systems and is dependent upon availability.

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Work-Stealing Scheduler

Allocates tasks dynamically to available processors, efficiently utilizing processors.

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Message Passing

A method where processors communicate by exchanging explicit messages to distribute a task.

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Performance Analysis

Evaluating how well a parallel program performs by calculating factors that affect its performance.

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Amdahl's Law

A formula that quantifies the theoretical speedup in a system with certain aspects parallelizable.

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Granularity

Describes the size and complexity of tasks in parallel programs. Small tasks mean high granularity, large tasks mean low granularity.

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Parallelism

The ability of multiple tasks to execute simultaneously to speed up a task.

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clEnqueueBarrier

A function in OpenCL that allows you to synchronize execution between different queues.

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Profiling interface

A feature in OpenCL that provides information about the performance of your OpenCL kernels and commands.

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cl_profiling_info values

Specific data points that the OpenCL profiling interface provides, such as the start time and end time of a kernel execution.

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OpenCL C for Compute Kernels

A specific subset of the C programming language specifically designed for writing OpenCL kernels.

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Language Highlights

Key features of OpenCL C that make it suitable for parallel programming on GPUs.

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Language Restrictions

Limitations imposed by OpenCL C to ensure efficient execution on different devices.

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Optional Extensions

Additional functionality that OpenCL implementations can provide beyond the standard.

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OpenGL Interoperability

OpenCL's ability to interact with OpenGL, facilitating seamless data transfer between the two APIs.

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OpenCL Programming

The process of writing, compiling, and executing OpenCL programs.

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Choosing Devices

The process of selecting appropriate hardware for your OpenCL program to run on.

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Create Memory Objects

The process of allocating memory on the GPU to store data used by OpenCL kernels.

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Memory Resources

Various memory allocation methods available in OpenCL, such as buffer memory or image memory.

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Transfer Data

The process of copying data between the host computer (CPU) and the GPU.

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Program Objects

A representation of an OpenCL program that contains code for your kernels.

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Kernel Execution configuration

Settings for how your OpenCL kernels are executed on the GPU, such as the number of work-items or work-groups.

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Event-Based Coordination

A method where events trigger actions in a coordinated manner, allowing tasks to be scheduled and executed based on specific occurrences.

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Single Program Multiple Data

A parallel programming pattern where a single program is executed on multiple data sets simultaneously.

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Multiple Program Multiple Data

A parallel programming pattern where multiple programs run on multiple data sets, allowing for independent processing and data exploration.

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Loop Parallelism Pattern

Divides the iterations of a loop among multiple processors to speed up execution, ideal for tasks that can be broken down into independent steps.

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Master/Worker Pattern

A structured parallel programming approach where a 'master' program distributes tasks to 'worker' programs, each processing data independently.

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Fork/Join Pattern

A pattern where tasks are divided into smaller units that can be run concurrently and later joined together to produce a final result.

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Map-Reduce

A parallel programming paradigm that efficiently processes large datasets, breaking tasks into independent 'map' and 'reduce' steps.

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Partitioning

Dividing data into smaller chunks for parallel processing, ensuring efficient data distribution among computing units.

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Communication

The transfer of data between processing units in a parallel computing environment, essential for coordinating work.

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Agglomeration

Combining intermediate results from multiple processors into a final result, often used in parallel algorithms.

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Bitonic Sequence

A sequence that can be divided into two monotonic subsequences (ascending and descending) that are concatenated in a specific order.

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Bitonic Sort

A sorting algorithm that efficiently sorts a bitonic sequence in parallel, taking advantage of bitonic sequence properties.

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Thrust

A C++ template library designed for efficient GPU programming, providing high-level functions to simplify parallel computations.

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Compiler Directives

Instructions embedded in code that guide the compiler to optimize code for parallel execution, leveraging resources like GPUs or multicore CPUs.

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OpenACC Directives

Special instructions added to code to tell the compiler how to parallelize tasks for execution on GPUs or other accelerators.

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Single Code for Multiple Platforms

OpenACC allows writing code that can run on different hardware platforms without significant changes, making it more versatile.

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Familiar to OpenMP Programmers

OpenACC uses a similar syntax and concepts to OpenMP, making it easier to learn for programmers familiar with that standard.

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Key OpenACC Advantage

OpenACC offers a true open standard, meaning it's not tied to a specific vendor or hardware platform.

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Kernels: OpenACC Directive

The kernels directive marks a section of code intended for execution on the accelerator.

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SAXPY Example

A simple mathematical operation (y = a * x + y) used to demonstrate how to implement parallelization with OpenACC.

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OpenACC parallel directive

Similar to kernels, but allows splitting a loop across multiple cores to run concurrently.

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OpenACC loop directive

Specifies that a loop should be parallelized by executing iterations in parallel, leveraging multiple cores.

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Study Notes

General Overview

  • Parallel programming involves multiple processors working simultaneously on a task.
  • This can significantly speed up computation, especially for large datasets or complex tasks.
  • There are several paradigms for parallel programming: data parallelism, task parallelism, and hybrid approaches merging the two.

Data Parallelism

  • Data parallelism operates on separate parts of a large dataset concurrently, such as elements in an array.
  • This approach works best when tasks operate independently on different data.
  • Data parallelism is often applied in matrix multiplication and image processing tasks.

Task Parallelism

  • Tasks that are independent of each other are performed by separate processes.
  • Each task is self contained and does not need to interact with other tasks.
  • The challenge for this method is managing the tasks, particularly for tasks that require complex synchronization.
  • The master/worker process and fork/join are examples of task parallelism.

Hybrid Approaches

  • Hybrid approaches combine data and task parallelism.
  • This can lead to better performance than individual methods, offering a better balance between resources and time.
  • Programmers can leverage methods suited to both data parallelism and task parallelism for the most performance.

Limitations of Parallelism

  • Communication overhead: data transfer between processing elements takes time.
  • Memory contention: shared resources become a bottleneck, increasing the workload and slow down of the process.
  • Data dependencies: if tasks depend on results from other tasks, this could limit the speed of execution.
  • Load imbalances: if the workload among tasks is uneven, then some tasks will finish first, while others are still working.

Memory Access Patterns

  • Uniform Memory Access (UMA): All processors have equal access to the memory. This makes tasks run more efficiently.
  • Non-Uniform Memory Access (NUMA): Different memory locations have different access times. This can hinder the ability of multiple tasks to run effectively and can limit performance.

Important Concepts

  • Work-Items: A small chunk of work performed on a single processor.
  • Synchronization: Mechanisms to coordinate and control the tasks to avoid race conditions.
  • Thread: A light weight, fundamental unit of work within a processing unit.
  • Concurrency: Where multiple tasks are in progress simultaneously. Crucial in parallel programming.
  • Pipelining: This involves breaking tasks into segments that are performed together by different units. This reduces the time taken for a complete computation.

OpenMP

  • OpenMP is a set of compiler directives that facilitate parallel programming.
  • It's beneficial for migrating existing sequential programs instead of rewriting entirely from scratch.
  • OpenMP is a popular method for parallelizing loop structures.

OpenACC

  • OpenACC is a compiler directive method that can offload computations on GPUs.
  • It can help developers to quickly implement parallelism of parts of their code.
  • It simplifies the process of parallelizing and optimizing code for multiple heterogeneous architectures.

Thrust

  • Thrust is a C++ template library allowing for vectorized and parallel computation on CPUs and GPUs.
  • It handles many of the low-level details of parallel computations, making it easier to utilize different hardware for optimized tasks.
  • Thrust is part of the NVIDIA CUDA SDK.

CUDA

  • CUDA is a parallel computing platform and application programming interface model.
  • It allows a developer to use a NVIDIA GPU for massively parallel computations.
  • Through CUDA, developers can control each thread and block to coordinate tasks and manage memory.

OpenCL

  • OpenCL is a standard API for programming parallel tasks over different hardware.
  • OpenCL offers portability between heterogeneous systems enabling a universal approach to parallel programming.

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