High-level transformation is the design activity in which loops are interchangeable. In this activity, loops are manipulated and transformed to optimize the code or improve its performance. Let's understand this in detail:

High-level transformation:
High-level transformation is a design activity where the algorithmic code is transformed to improve its performance, reduce resource usage, or optimize it for a specific target platform. It involves various transformations like loop interchange, loop unrolling, loop fusion, loop distribution, etc.

Interchangeability of loops:
Loop interchange is a transformation where the order of nested loops is changed. This transformation is possible when the loops are independent of each other and do not have any data dependencies. By interchanging loops, the computation can be distributed differently, which may lead to improved performance or better resource utilization.

Benefits of loop interchange:
Loop interchange can provide several benefits, including:

1. Improved cache utilization: By changing the order of nested loops, the memory access patterns can be optimized, leading to better cache utilization. This can result in reduced memory latency and improved overall performance.

2. Parallelization opportunities: Interchangeable loops can enable parallel execution of the code. By interchanging the loops, the computation can be distributed across multiple processing units, allowing for better utilization of parallel resources.

3. Reduction in loop overhead: Loop interchange can eliminate redundant computations and reduce loop overhead. This can result in faster execution and improved efficiency of the code.

Example:
Consider the following code snippet:

```
for (i = 0; i < n;="" i++)="" />
for (j = 0; j < m;="" j++)="" />
// computation
}
}
```

In this code, the outer loop iterates over variable `i` and the inner loop iterates over variable `j`. If these loops are interchangeable, we can interchange them as follows:

```
for (j = 0; j < m;="" j++)="" />
for (i = 0; i < n;="" i++)="" />
// computation
}
}
```

By interchanging the loops, we may achieve better cache utilization or parallelization opportunities, depending on the specific context and requirements of the code.

Conclusion:
In the design activity of high-level transformation, loops are interchangeable. Loop interchange is a powerful transformation that can optimize code performance, improve cache utilization, enable parallelization, and reduce loop overhead.