opencv path error in mxnet scala tutorial

[jesterhazy]

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Description

The mxnet scala in intellij instructions at http://mxnet.incubator.apache.org/tutorials/scala/mxnet_scala_on_intellij.html do not work because of an opencv library path error.

Package used (Python/R/Scala/Julia):
mxnet-scala

For Scala user, please provide:
1. Java version: 1.8.0_171
2. Maven version:  3.3.9 
3. Scala runtime if applicable: 2.11.8

Error Message:

Exception in thread "main" java.lang.UnsatisfiedLinkError: /private/var/folders/nz/57cdgtr11pdg01rgzyzhjxvmqwmxjn/T/mxnet4117240061172168094/mxnet-scala: dlopen(/private/var/folders/nz/57cdgtr11pdg01rgzyzhjxvmqwmxjn/T/mxnet4117240061172168094/mxnet-scala, 1): Library not loaded: /usr/local/opt/opencv/lib/libopencv_stitching.3.4.dylib
  Referenced from: /private/var/folders/nz/57cdgtr11pdg01rgzyzhjxvmqwmxjn/T/mxnet4117240061172168094/mxnet-scala
  Reason: image not found
    at java.lang.ClassLoader$NativeLibrary.load(Native Method)
    at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1941)
    at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1824)
    at java.lang.Runtime.load0(Runtime.java:809)
    at java.lang.System.load(System.java:1086)
    at org.apache.mxnet.util.NativeLibraryLoader$.loadLibraryFromStream(NativeLibraryLoader.scala:140)
    at org.apache.mxnet.util.NativeLibraryLoader$.loadLibrary(NativeLibraryLoader.scala:93)
    at org.apache.mxnet.Base$.<init>(Base.scala:70)
    at org.apache.mxnet.Base$.<clinit>(Base.scala)
    at org.apache.mxnet.NDArray$.initNDArrayModule(NDArray.scala:151)
    at org.apache.mxnet.NDArray$.<init>(NDArray.scala:38)
    at org.apache.mxnet.NDArray$.<clinit>(NDArray.scala)
    at mxnet.App$.delayedEndpoint$mxnet$App$1(App.scala:9)
    at mxnet.App$delayedInit$body.apply(App.scala:6)
    at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App$$anonfun$main$1.apply(App.scala:76)
    at scala.App$$anonfun$main$1.apply(App.scala:76)
    at scala.collection.immutable.List.foreach(List.scala:381)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
    at scala.App$class.main(App.scala:76)
    at mxnet.App$.main(App.scala:6)
    at mxnet.App.main(App.scala)

Steps to reproduce

1. Follow tutorial to "Step 7. Run Sample MXNet Code in the App" and run the app
2. App fails with stack trace shown above.

What have you tried to solve it?

1. Replacing the brew install opencv@2 command in the mac prequisite setup section with brew install opencv fixes the problem and lets the example app run successfully. So either the example doc needs to be revised to use the other opencv version, or mxnet scala needs to look for different lib path.

[jesterhazy]

@aaronmarkham @lanking520

[anirudhacharya]

@mxnet-label-bot [Scala, Example]

[lanking520]

@jesterhazy in 1.2.0 we used opencv@2, 1.2.1 we used opencv (version 3)

[lanking520]

Hi @jesterhazy did this solve your problem?

[jesterhazy]

@lanking520 i figured out the workaround before i opened the ticket (as noted in the ticket). the problem is that the instructions are wrong.

[lanking520]

@jesterhazy thank you. @aaronmarkham can you pick up from here and update the installation instruction for Scala user?

[zachgk]

This issue can be closed as it was resolved in #12654

[zachgk]

@lanking520 We can close this issue because the fix was applied in #12654

[lanking520]

@jesterhazy Let's close this issue for now since all of our new releases are static-linked. We no longer require user to install OpenCV in the system. Please feel free to reopen if you still find this problems in our releases