add disable static option in DJL to allow some model running (#1735)

docs/mxnet/how_to_convert_your_model_to_symbol.md

@@ -14,7 +14,7 @@ net.add(nn.Dense(10))
 
 # initialize and hybridize the block
 net.initialize()
-net.hybridize()
+net.hybridize(static_alloc=True, static_shape=True)
 
 # create sample input and run forward once
 x = nd.random.uniform(shape=(2, 20))
@@ -36,7 +36,7 @@ from gluoncv import model_zoo
 
 # get the pretrained model from the gluon model zoo
 net = model_zoo.get_model('resnet18_v1', pretrained=True)
-net.hybridize()
+net.hybridize(static_alloc=True, static_shape=True)
 
 # create a sample input and run forward once (required for tracing)
 x = nd.random.uniform(shape=(1, 3, 224, 224))
@@ -45,3 +45,22 @@ net(x)
 # export your model
 net.export("sample_model")
 ```
+
+### hybridize without `static_alloc=True, static_shape=True`
+
+It is always recommended enabling the static settings when exporting Apache MXNet model. This will ensure DJL to have the best performance for inference.
+
+If you run hybridize without `static_alloc=True, static_shape=True`:
+
+```
+net.hybridize()
+```
+
+you can enable this Java property with DJL:
+
+```
+-Dai.djl.mxnet.static_alloc=False -Dai.djl.mxnet.static_shape=False
+```
+
+This will ensure we skip the static settings in the inference model and make DJL produce consistent result with Python.
+

engines/mxnet/mxnet-engine/src/main/java/ai/djl/mxnet/jna/JnaUtils.java

@@ -1887,8 +1887,18 @@ public static CachedOp createCachedOp(
         PointerByReference ref = REFS.acquire();
 
         // static_alloc and static_shape are enabled by default
+        String staticAlloc = "1";
+        String staticShape = "1";
+        if (!Boolean.parseBoolean(System.getProperty("ai.djl.mxnet.static_alloc", "true"))) {
+            staticAlloc = "0";
+        }
+        if (!Boolean.parseBoolean(System.getProperty("ai.djl.mxnet.static_shape", "true"))) {
+            staticShape = "0";
+        }
         String[] keys = {"data_indices", "param_indices", "static_alloc", "static_shape"};
-        String[] values = {dataIndices.values().toString(), paramIndices.toString(), "1", "1"};
+        String[] values = {
+            dataIndices.values().toString(), paramIndices.toString(), staticAlloc, staticShape
+        };
 
         checkCall(LIB.MXCreateCachedOpEx(symbolHandle, keys.length, keys, values, ref));
         Pointer pointer = ref.getValue();