In lisp, how can I measure and record the time taken to evaluate an expression?

Question

I want to get the results of the time macro call in order to collect several measurements and process them. I tried the locally setf standard output and redirected it to a string, but it did not work with the time macro. This may be wrong, but I tried:

 (with-output-to-string (str) (let ((*standard-output* str)) (time (test-with-size 40)))) 

Questions:

• Is there a way to capture the output of time ?
• If not, can I capture the output of the slime-profile-report command?
• If none of the above works, how can I measure the time spent evaluating an arbitrary expression?

I want to measure the execution time of an algorithm as the input size increases for each input size (from 1 to 100). I will measure many times and keep the average value. Then I want to build the results. The continuity is simple, and I found many ways in Cliki, but how can I collect the results?

I use CLISP and CCL.

EDIT: Paul Nathan pointed out that the time macro outputs to *trace-output* , which is the solution. I would like to get a more pleasant and simple solution, because with this I have to deal with implementation-specific tracing.

Answer 1

If you want to capture text, you need to use the correct stream. The ANSI CL standard says TIME prints for trace output.

So this will give you text as a string.

 (with-output-to-string (*trace-output*) (time (sin 40.0))) 

You can also write your own macro using time primitives. See 25.1.4.3 Internal time for numerical data.