Vectorize this update loop. Call the function `update`: import numpy as np def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high
Vectorize this update loop. Call the function `update`: import numpy as np def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high
We can avoid the explicit for‐loop by taking advantage of NumPy's element‐wise operations. Notice that for indices i ≠ highest_number, we want to update high[i] = min(high[i], high[highest_number] + delta[highest_number] − delta[i]). A vectorized solution computes the candidate value for all indices in one go, then uses a boolean mask to update only those indices that are not equal to highest_number. For example: -------------------------------------------------- import numpy as np def update(high, highest_number, delta): # Compute the candidate update for each element: candidate = high[highest_number] + delta[highest_number] - delta # Create a boolean mask for indices that are not highest_number: mask = np.arange(len(high)) != highest_number # Update the values using np.minimum elementwise: high[mask] = np.minimum(high[mask], candidate[mask]) return high # Example usage: high = np.array([10, 5, 8, 20]) delta = np.array([1, 2, 3, 4]) highest_number = 3 print(update(high, highest_number, delta)) -------------------------------------------------- Explanation: 1. candidate is a NumPy array computed as high[highest_number] + delta[highest_number] subtracted by the array delta. 2. The mask is a boolean array that is True for all indices except highest_number. 3. np.minimum is applied element‐wise to update only the desired indices. 4. We preserve the value at index highest_number. This achieves the same result as the loop but using vectorized NumPy operations.
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 | import numpy as np def update(high, highest_number, delta): # Compute the candidate update for each element: candidate = high[highest_number] + delta[highest_number] - delta # Create a boolean mask for indices that are not highest_number: mask = np.arange(len(high)) != highest_number # Update the values using np.minimum elementwise: high[mask] = np.minimum(high[mask], candidate[mask]) return high |
Below is a student's answer to a question about how to vectorize this loop: def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high Here is their code: import numpy as np def update(high, highest_number, delta): # Compute the candidate update for each element: candidate = high[highest_number] + delta[highest_number] - delta # Create a boolean mask for indices that are not highest_number: mask = np.arange(len(high)) != highest_number # Update the values using np.minimum elementwise: high[mask] = np.minimum(high[mask], candidate[mask]) return high Did the student try to vectorize the loop? Don't tell me if they are correct or not. (I have tests for that separately which will catch any bugs.) Just tell me if they tried to vectorize the loop. End your answer with either the string "The student passes" if they tried to do a vectorized loop, or "The student fails" if they just wrote a for loop again.
The student's code uses NumPy operations (like creating a boolean mask, and directly computing a vectorized candidate array) instead of a loop, which shows they attempted to vectorize the loop. The student passes
Testing if the previous output contains the string student passes
: True
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | import numpy as np def update(high, highest_number, delta): # Compute the candidate update for each element: candidate = high[highest_number] + delta[highest_number] - delta # Create a boolean mask for indices that are not highest_number: mask = np.arange(len(high)) != highest_number # Update the values using np.minimum elementwise: high[mask] = np.minimum(high[mask], candidate[mask]) return high import numpy as np answer = list(update(np.array([2, 5, 9, 1, 2, 0, 3, 8]), 4, np.array([1, 2, 1, 4, 3, 2, 1, 2]))) expected = [2, 3, 4, 1, 2, 0, 3, 3] assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
All tests passed
Testing if the previous output contains the string All tests passed
: True
Vectorize this update loop. Call the function `update`: import numpy as np def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high
Vectorize this update loop. Call the function `update`: import numpy as np def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high
You can replace the loop with a vectorized operation using Boolean indexing. The idea is to create a mask that selects all indices except the one corresponding to highest_number, compute the new values for those indices, and then update them with the minimum between the current value and the new computed value. Here's one way to do it: ------------------------------------------------------------ import numpy as np def update(high, highest_number, delta): # Create a mask that is True for all indices except 'highest_number' mask = np.arange(len(high)) != highest_number # Compute for each index: high[highest_number] + delta[highest_number] - delta[i] new_values = high[highest_number] + delta[highest_number] - delta[mask] # Update only the indices in 'high' (except highest_number) with the minimum of # the current value and the new value high[mask] = np.minimum(high[mask], new_values) return high # Example usage: high = np.array([10, 20, 30, 40]) delta = np.array([1, 2, 3, 4]) highest_number = 2 # For example, choose index 2 as the highest print(update(high, highest_number, delta)) ------------------------------------------------------------ Explanation: 1. We generate a Boolean mask that excludes the selected highest_number index. 2. For the positions given by the mask, we compute the term high[highest_number] + delta[highest_number] - delta[i]. 3. We use np.minimum to compare and update the elements of high accordingly. 4. The function returns the updated high array. This approach avoids the explicit Python loop and runs the operation in a vectorized manner using NumPy.
I extracted the following code from that output:
1 2 3 4 5 6 7 8 9 10 11 12 13 | import numpy as np def update(high, highest_number, delta): # Create a mask that is True for all indices except 'highest_number' mask = np.arange(len(high)) != highest_number # Compute for each index: high[highest_number] + delta[highest_number] - delta[i] new_values = high[highest_number] + delta[highest_number] - delta[mask] # Update only the indices in 'high' (except highest_number) with the minimum of # the current value and the new value high[mask] = np.minimum(high[mask], new_values) return high |
Below is a student's answer to a question about how to vectorize this loop: def update(high, highest_number, delta): for i in range(len(high)): if i != highest_number: high[i] = min(high[i], high[highest_number] + delta[highest_number] - delta[i]) return high Here is their code: import numpy as np def update(high, highest_number, delta): # Create a mask that is True for all indices except 'highest_number' mask = np.arange(len(high)) != highest_number # Compute for each index: high[highest_number] + delta[highest_number] - delta[i] new_values = high[highest_number] + delta[highest_number] - delta[mask] # Update only the indices in 'high' (except highest_number) with the minimum of # the current value and the new value high[mask] = np.minimum(high[mask], new_values) return high Did the student try to vectorize the loop? Don't tell me if they are correct or not. (I have tests for that separately which will catch any bugs.) Just tell me if they tried to vectorize the loop. End your answer with either the string "The student passes" if they tried to do a vectorized loop, or "The student fails" if they just wrote a for loop again.
Yes, the student is indeed trying to vectorize the loop by using NumPy's array indexing and vectorized operations instead of a Python for loop. The student passes
Testing if the previous output contains the string student passes
: True
Running the following program:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 | import numpy as np def update(high, highest_number, delta): # Create a mask that is True for all indices except 'highest_number' mask = np.arange(len(high)) != highest_number # Compute for each index: high[highest_number] + delta[highest_number] - delta[i] new_values = high[highest_number] + delta[highest_number] - delta[mask] # Update only the indices in 'high' (except highest_number) with the minimum of # the current value and the new value high[mask] = np.minimum(high[mask], new_values) return high import numpy as np answer = list(update(np.array([2, 5, 9, 1, 2, 0, 3, 8]), 4, np.array([1, 2, 1, 4, 3, 2, 1, 2]))) expected = [2, 3, 4, 1, 2, 0, 3, 3] assert answer == expected, f'Wrong answer; got {answer} instead of {expected}' print('All tests passed') |
All tests passed
Testing if the previous output contains the string All tests passed
: True