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RobotLocomotion
doc: Need to improve docs for CMake build options (e.g. SNOPT)
Per slack convo: https://drakedevelopers.slack.com/archives/C3YB3EV5W/p1570643928005400
hongkai.dai Today at 1:58 PM
When I build drake python binding with -DWITH_SNOPT=ON. But I got the error saying that SNOPT source archive was NOT found at 'SNOPT_PATH-NOTFOUND'. I have set SNOPT_PATH=git but it doesn't help
eric.cousineau 1 hour ago
Was a bit confused by this too; apparently this has different semantics than Bazel.
If you want the equivalent of SNOPT_PATH=git in Bazel, then you should pass -DWITH_ROBOTLOCOMOTION_SNOPT=ON.
If you want the equivalent usage of SNOPT_PATH, you have to explicitly pass it as -DSNOPT_PATH, the CMakeLists.txt is not built to look at env variables.
\cc @jamiesnape (edited)
hongkai.dai 1 hour ago
Got it, thanks!
hongkai.dai 1 hour ago
It would be helpful if we mention how to build with SNOPT in https://drake.mit.edu/python_bindings.html#building-the-python-bindings
eric.cousineau 1 hour ago
Yeah, better docs would help.
I think it's kinda weird that we have those instructions in the Python binding instructions... I'll see if there's a way to put those instructions in a more sensical location, and xref.
I can try to get to that next week.
\cc @jamiesnape
Still fine to improve the documentation, but a general tip: if you're not sure how to pass options to cmake, run ccmake instead and browse through the user interface. It works well.
Even updating the existing documentation would help, perhaps with a note that it will be improved later. I just got bit by this issue and was totally puzzled until I finally came accross this issue. A small note in the documentation would have helped.
This just bit me again today. Was following the instructions for building bindings and got the same error as Hongkai.
Just ran into this issue as well.
It appears that the CMake file sets SNOPT_PATH to "SNOPT_PATH-NOTFOUND", like the string literal (unless I'm misunderstanding both the set function and the error message).
I was able to fix it with a 1-line change to CMakeLists.txt (see patch below) that pulls from the environment variable instead (as per the documentation).
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -484,7 +484,7 @@ if(WITH_ROBOTLOCOMOTION_SNOPT OR WITH_SNOPT)
if(WITH_ROBOTLOCOMOTION_SNOPT)
string(APPEND BAZEL_REPO_ENV " --repo_env=SNOPT_PATH=git")
else()
- set(SNOPT_PATH SNOPT_PATH-NOTFOUND CACHE FILEPATH
+ set(SNOPT_PATH "$ENV{SNOPT_PATH}" CACHE FILEPATH
"Path to SNOPT source archive"
)
if(NOT EXISTS "${SNOPT_PATH}")
Fixed in #22461. The https://drake.mit.edu/from_source.html now explains all of the CMake options.