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metal : fix graph capture and handle empty graphs - #29390
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- return early when the graph has no nodes - drop the redundant reset of capture_compute: the decrement at the top of the function already transitions the counter from 0 to -1, so a capture happens exactly once - hint at METAL_CAPTURE_ENABLED=1 in the capture error message - pass capture_compute == 0 (not the raw counter) as use_capture to ggml_metal_op_init, so GPU debug-group markers are only emitted on the captured compute Assisted-by: pi:llama.cpp/Qwen3.8-27B
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- return early when the graph has no nodes - drop the redundant reset of capture_compute: the decrement at the top of the function already transitions the counter from 0 to -1, so a capture happens exactly once - hint at METAL_CAPTURE_ENABLED=1 in the capture error message - pass capture_compute == 0 (not the raw counter) as use_capture to ggml_metal_op_init, so GPU debug-group markers are only emitted on the captured compute Assisted-by: pi:llama.cpp/Qwen3.8-27B
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- return early when the graph has no nodes - drop the redundant reset of capture_compute: the decrement at the top of the function already transitions the counter from 0 to -1, so a capture happens exactly once - hint at METAL_CAPTURE_ENABLED=1 in the capture error message - pass capture_compute == 0 (not the raw counter) as use_capture to ggml_metal_op_init, so GPU debug-group markers are only emitted on the captured compute Assisted-by: pi:llama.cpp/Qwen3.8-27B (cherry picked from commit 84e76d8)
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Overview
Small fixes to the Metal graph capture path in
ggml_metal_graph_compute:GGML_STATUS_SUCCESSearly when the graph has no nodes, avoiding the command-buffer/capture machinery for an empty graph.ctx->capture_compute: the decrement at the top of the function already transitions the counter from0to-1, so a capture happens exactly once (whether or not the capture scope starts successfully).did you set METAL_CAPTURE_ENABLED=1 ?hint in the capture error message.ctx->capture_compute == 0(rather than the raw counter) as theuse_captureargument toggml_metal_op_init. The counter is a countdown, so any non-zero value (including-1after the first compute) coerced totrueand caused per-node GPU debug-group markers to be emitted on every compute instead of only on the captured one.Requirements