parallel_stereo with asp_mgm `/bin/sh: free: command not found`

[dshean]

Describe the bug Running parallel_stereo with asp_mgm on latest daily build with sample frame camera images and RPC session. Each tile produces:

/bin/sh: free: command not found Warning: Error checking system memory, skipping the memory test!

To Reproduce Steps to reproduce the behavior: parallel_stereo --stereo-algorithm asp_mgm --corr-kernel 7 7 *pan.tif mgm_rpc/mgm_rpc

Expected behavior I think this is all just for SGM/MGM memory consumption estimate, which I know was somewhat experimental. Don't want to assume free utility is installed by default.

Your Environment (please complete the following information):

• OS: [e.g. macOS, Linux, and their version number]

  Darwin 19.6.0 Darwin Kernel Version 19.6.0: Tue Feb 15 21:39:11 PST 2022; root:xnu-6153.141.59~1/RELEASE_X86_64 x86_64 i386 iMacPro1,1 Darwin

• ASP Version: [e.g. 2.6.2, can find via stereo --version]

  NASA Ames Stereo Pipeline 3.0.1-alpha Build ID: 39a1cf2e Build date: 2022-04-27

  Built against: NASA Vision Workbench 3.0.0 Build ID: a717c7e2 USGS ISIS 5.0.1 Boost C++ Libraries 106800 GDAL 2.4.1 | 20190315

[oleg-alexandrov]

Since when do you expect anything 'free' on the Mac? Or even cheap?

I put a fix in https://github.com/NeoGeographyToolkit/StereoPipeline/commit/11fae82909f6434556132faebd249d0d198c54ba.

Thanks. The moral: Use Linux.