Classification: Confidential Region. The Optimizer takes a whole lot of virtual storage
-----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Charles Mills Sent: Friday, March 14, 2025 1:39 PM To: [email protected] Subject: Open XL C dramaticallly slower thant z/OS XL C compiler - expected? [CAUTION: This Email is from outside the Organization. Unless you trust the sender, Don’t click links or open attachments as it may be a Phishing email, which can steal your Information and compromise your Computer.] I am trying to get started with the new, "open," Clang-based XLC compiler. I am stunned at how noticeably slower it is than the legacy C compiler. I wasn't looking to benchmark -- the slow compile times just jumped out at me. Is this to be expected? I wish I had numbers for exactly the same source code but there are different userids involved and it's a little complicated. Different options for the two compiles because the option specifications are incompatible. Both modules are fairly vanilla source code written by the same author. Both of the following are on the same machine, the same virtual machine at IBM Dallas. It's a z16 A01. Compile under the legacy XL C compiler, a C++ compile of a 1886-line source module: 4 seconds elapsed, .36 CPU seconds. Compile under Open XL C compiler, a C++ compile of a 415-line source module: 26 seconds elapsed, 1.32 CPU seconds. Is this what others are seeing? Is this to be expected? IS anyone using the new compiler? Charles ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ::DISCLAIMER:: ________________________________ The contents of this e-mail and any attachment(s) are confidential and intended for the named recipient(s) only. E-mail transmission is not guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or may contain viruses in transmission. The e mail and its contents (with or without referred errors) shall therefore not attach any liability on the originator or HCL or its affiliates. Views or opinions, if any, presented in this email are solely those of the author and may not necessarily reflect the views or opinions of HCL or its affiliates. Any form of reproduction, dissemination, copying, disclosure, modification, distribution and / or publication of this message without the prior written consent of authorized representative of HCL is strictly prohibited. If you have received this email in error please delete it and notify the sender immediately. Before opening any email and/or attachments, please check them for viruses and other defects. ________________________________ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
