Blitz++ 矩阵相乘(张量运算) 示例

最新推荐文章于 2025-11-16 12:57:56 发布

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最新推荐文章于 2025-11-16 12:57:56 发布 · 4.6k 阅读

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#matrix #permutation #iostream #float #types #function

本文介绍了使用Blitz++库进行矩阵相乘和张量运算的具体示例，展示了4x4矩阵B和D的元素及运算过程，涉及矩阵的初始化、类型定义以及输入输出操作。

//整理 by RobinKin

//Blitz++ 张量计算的示例

/*****************************************************************************
 * matmult.cpp     Blitz++ tensor notation example
 *****************************************************************************
 * This example illustrates the tensor-like notation provided by Blitz++.
 */

#include <blitz/array.h>
#include <iostream>

using namespace blitz;

int main()
{
    // Create two 4x4 arrays.  We want them to look like matrices, so
    // we'll make the valid index range 1..4 (rather than 0..3 which is
    // the default).

    Range r(1,4);
    Array<float,2> A(r,r), B(r,r);

    // The first will be a Hilbert matrix:
    //
    // a   =   1
    //  ij   -----
    //       i+j-1
    //
    // Blitz++ provides a set of types { firstIndex, secondIndex, ... }
    // which act as placeholders for indices.  These can be used directly
    // in expressions.  For example, we can fill out the A matrix like this:

    firstIndex i;    // Placeholder for the first index
    secondIndex j;   // Placeholder for the second index

    A = 1.0 / (i+j-1);

    cout << "A = " << A << endl;

    // A = 4 x 4
    //         1       0.5  0.333333      0.25
    //       0.5  0.333333      0.25       0.2
    //  0.333333      0.25       0.2  0.166667
    //      0.25