fix: report VRAM usage across all GPUs instead of only the default device (#169)

memory_allocated() and memory_reserved() without a device argument only
report GPU 0. Sum across all devices for correct multi-GPU totals and
add total VRAM reporting.

src/heretic/main.py

@@ -174,9 +174,15 @@ def run():
     # Adapted from https://github.com/huggingface/accelerate/blob/main/src/accelerate/commands/env.py
     if torch.cuda.is_available():
         count = torch.cuda.device_count()
-        print(f"Detected [bold]{count}[/] CUDA device(s):")
+        total_vram = sum(torch.cuda.mem_get_info(i)[1] for i in range(count))
+        print(
+            f"Detected [bold]{count}[/] CUDA device(s) ({total_vram / (1024**3):.2f} GB total VRAM):"
+        )
         for i in range(count):
-            print(f"* GPU {i}: [bold]{torch.cuda.get_device_name(i)}[/]")
+            vram = torch.cuda.mem_get_info(i)[1] / (1024**3)
+            print(
+                f"* GPU {i}: [bold]{torch.cuda.get_device_name(i)}[/] ({vram:.2f} GB)"
+            )
     elif is_xpu_available():
         count = torch.xpu.device_count()
         print(f"Detected [bold]{count}[/] XPU device(s):")

src/heretic/utils.py

@@ -38,11 +38,17 @@ def print_memory_usage():
     p("Resident system RAM", Process().memory_info().rss)
 
     if torch.cuda.is_available():
-        p("Allocated GPU VRAM", torch.cuda.memory_allocated())
+        count = torch.cuda.device_count()
-        p("Reserved GPU VRAM", torch.cuda.memory_reserved())
+        allocated = sum(torch.cuda.memory_allocated(device) for device in range(count))
+        reserved = sum(torch.cuda.memory_reserved(device) for device in range(count))
+        p("Allocated GPU VRAM", allocated)
+        p("Reserved GPU VRAM", reserved)
     elif is_xpu_available():
-        p("Allocated XPU memory", torch.xpu.memory_allocated())
+        count = torch.xpu.device_count()
-        p("Reserved XPU memory", torch.xpu.memory_reserved())
+        allocated = sum(torch.xpu.memory_allocated(device) for device in range(count))
+        reserved = sum(torch.xpu.memory_reserved(device) for device in range(count))
+        p("Allocated XPU memory", allocated)
+        p("Reserved XPU memory", reserved)
     elif torch.backends.mps.is_available():
         p("Allocated MPS memory", torch.mps.current_allocated_memory())
         p("Driver (reserved) MPS memory", torch.mps.driver_allocated_memory())