misc: Add multiple machine example (#757)

This is a more exotic example of multi env usage

---------

Co-authored-by: Wackyator <[email protected]>

examples/multi-machine/.gitattributes

@@ -0,0 +1,2 @@
+# GitHub syntax highlighting
+pixi.lock linguist-language=YAML

examples/multi-machine/.gitignore

@@ -0,0 +1,2 @@
+# pixi environments
+.pixi

examples/multi-machine/pixi.toml

@@ -0,0 +1,47 @@
+[project]
+name = "multi-machine"
+description = "A mock project that does ML stuff"
+channels = ["conda-forge", "pytorch"]
+# All platforms that are supported by the project as the features will take the intersection of the platforms defined there.
+platforms = ["win-64", "linux-64", "osx-64", "osx-arm64"]
+
+[tasks]
+train = "python train.py"
+test = "python test.py"
+start = {depends_on = ["train", "test"]}
+
+[dependencies]
+python = "3.11.*"
+pytorch = {version = ">=2.0.1", channel = "pytorch"}
+torchvision = {version = ">=0.15", channel = "pytorch"}
+polars = ">=0.20,<0.21"
+matplotlib-base = ">=3.8.2,<3.9"
+ipykernel = ">=6.28.0,<6.29"
+
+[feature.cuda]
+platforms = ["win-64", "linux-64"]
+channels = ["nvidia", {channel = "pytorch", priority = -1}]
+system-requirements = {cuda = "12.1"}
+
+[feature.cuda.tasks]
+train = "python train.py --cuda"
+test = "python test.py --cuda"
+
+[feature.cuda.dependencies]
+pytorch-cuda = {version = "12.1.*", channel = "pytorch"}
+
+[feature.mlx]
+platforms = ["osx-arm64"]
+system-requirements = {macos = "13.3"}
+
+[feature.mlx.tasks]
+train = "python train.py --mlx"
+test = "python test.py --mlx"
+
+[feature.mlx.dependencies]
+mlx = "*"
+
+
+[environments]
+cuda = ["cuda"]
+mlx = ["mlx"]

examples/multi-machine/test.py

@@ -0,0 +1,8 @@
+import os
+import sys
+
+print("Hello from test.py!")
+print("Environment you are running on:")
+print(os.environ["PIXI_ENVIRONMENT_NAME"])
+print("Arguments given to the script:")
+print(sys.argv[1:])

examples/multi-machine/train.py

@@ -0,0 +1,24 @@
+import os
+import sys
+
+if os.environ["PIXI_ENVIRONMENT_NAME"] == "mlx":
+    import mlx.core as mx
+    a = mx.array([1, 2, 3, 4])
+    print(a.shape)
+    print("MLX is available, in mlx environment as expected")
+
+if os.environ["PIXI_ENVIRONMENT_NAME"] == "cuda":
+    import torch
+    assert torch.cuda.is_available(), "CUDA is not available"
+    print("CUDA is available, in cuda environment as expected")
+
+if os.environ["PIXI_ENVIRONMENT_NAME"] == "default":
+    import torch
+    assert not torch.cuda.is_available(), "CUDA is available, in default environment"
+    print("CUDA is not available, in default environment as expected")
+
+print("\nHello from train.py!")
+print("Environment you are running on:")
+print(os.environ["PIXI_ENVIRONMENT_NAME"])
+print("Arguments given to the script:")
+print(sys.argv[1:])

examples/opencv/webcam_capture.py

@@ -21,16 +21,25 @@ def capture_and_grayscale():
     # Load the cascade for face detection
     face_cascade = cv2.CascadeClassifier(filename)
 
-    # Connect to the webcam
-    cap = cv2.VideoCapture(0)
+    # Search for available webcams
+    working_cam = None
+    for index in range(3):
+        cap = cv2.VideoCapture(index)
+        if not cap.read()[0]:
+            cap.release()
+            continue
+        else:
+            working_cam = cap
+            break
+
 
     # Check if the webcam is opened correctly
-    if not cap.isOpened():
+    if not working_cam.isOpened():
         raise IOError("Cannot open webcam")
 
     while True:
         # Read the current frame from the webcam
-        ret, frame = cap.read()
+        ret, frame = working_cam.read()
 
         if not ret:
             break
@@ -57,7 +66,7 @@ def capture_and_grayscale():
             break
 
     # Release the VideoCapture object
-    cap.release()
+    working_cam.release()
 
     # Destroy all windows
     cv2.destroyAllWindows()