<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12pt"><div>Hello,</div><div> </div><div>I am using serial PETSc linear solver in a serial Fortran program, which uses function CPU_TIME() to count cpu time. In Windows-7, the cpu time turns out to be 2 to 3 times as much as elapse time. My questions are:</div><div> </div><div>1. Does PETSc internally use multi-thread even though I configured it with --useThreads=0? I ask so since it is known that CPU_TIME() adds the cpu time of all threads togather.</div><div>2. The same program gets consistent cpu time and elapse time in Linux. Do you have any idea why?</div><div> </div><div>Thanks for any suggestions.</div><div>Qin</div></div></body></html>