The problem was that the print operations was being done character-by-character and it resulted in the printing being a significant overhead in the execution of the tests themselves. With this change they saw a speed up of many times simply because it was using buffered output.
https://github.com/apple/swift/commit/259d57bbe7784955108caa...
The problem was that the print operations was being done character-by-character and it resulted in the printing being a significant overhead in the execution of the tests themselves. With this change they saw a speed up of many times simply because it was using buffered output.