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void showOpenCVMat(cv::Mat img, UIImageView* imageView) {
  cv::Mat converted;
  img.convertTo(converted, CV_8U);
  // convert the cv::Mat to UIImage
  NSData *data = [NSData dataWithBytes:converted.data length:converted.elemSize() * converted.total()];
  CGColorSpaceRef colorSpace =
      CGColorSpaceCreateDeviceGray();  // CGColorSpaceCreateDeviceRGB();
  CGDataProviderRef provider =
      CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
  CGImageRef imageRef = CGImageCreate(

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基本版本

class Singleton {
  Singleton() = default;

 public:
  Singleton(const Singleton&)            = delete;
  Singleton& operator=(const Singleton&) = delete;

ZJUGuoShuai

C++ STL 中的 std::swap 通常是如何实现的？

C++11 之前，只能使用拷贝构造和拷贝赋值：

template <typename T>
void swap(T& a, T& b) {
  T t = a;
  b = a;
 b = t;

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template <typename T>
class vector {
  size_t size_     = 0;
  size_t capacity_ = 0;
  T* data_         = nullptr;

 public:
  // Default constructor
  vector() = default;

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def sample(img, x: float, y: float):
    h, w = img.shape

    left = math.floor(x)
    top = math.floor(y)
    right = left + 1
    bottom = top + 1

    # top left corner
    if (0 <= left < w) and (0 <= top < h):

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#include <limits>
#include <iostream>

int main() {
    float eps = std::numeric_limits<float>::epsilon();
    float a = 1.0f;
    float b = a + eps;
    float c = a + eps / 2.0f;
    std::cout << "a == b: " << std::boolalpha << (a == b) << "\n";  // false
    std::cout << "a == c: " << std::boolalpha << (a == c) << "\n";  // true

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给 ComputeShader class 增加以下三个方法：

// 从 OpenCV Mat 创建（只读的） Metal Texture
- (id<MTLTexture>) textureFromCVMat:(const void*)cv_data Width:(int) w Height:(int)h {
  // Create a Metal texture descriptor
  MTLTextureDescriptor *textureDescriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:MTLPixelFormatR8Unorm
                                                                                               width:w
                                                                                              height:h
                                                                                           mipmapped:NO];

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import Cocoa

let input: [Float] = [0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0]
var output_real = Array<Float>(repeating: 0, count: 8)
var output_imag = Array<Float>(repeating: 0, count: 8)

for i in 0..<8 {
    var real_sum: Float = 0.0
    var imag_sum: Float = 0.0
    for k in 0..<8 {

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//
//  Timer.h
//  NLE
//
//  Created by Guo Shuai on 2023/7/27.
//

#ifndef Timer_h
#define Timer_h

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#include <stdio.h>
#include <math.h>

#define PI 3.14159265358979323846

// O(n^2)
void dft(double *input, double *real, double *imag, int n) {
    for (int k = 0; k < n; k++) {
        real[k] = 0;
        imag[k] = 0;