[Temporary Workaround] Fix pipelined sampling corruption: use per-call execution descriptor#121
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The MPSGraphCompositeSampler reused a single MPSGraphExecutableExecutionDescriptor across all pipelined steps. Under pipelined execution (depth > 1), overlapping runAsync calls on the same executable corrupt intermediate scratch buffers when sharing a descriptor, producing garbled output (word repetitions, doubled punctuation) with temperature > 0. Create a fresh descriptor per encode() call, matching the pattern MPSGraphArgmaxSampler already uses.
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The MPSGraphCompositeSampler reused a single
MPSGraphExecutableExecutionDescriptor across all pipelined steps. Under pipelined execution (depth > 1), overlapping runAsync calls on the same executable corrupt intermediate scratch buffers when sharing a descriptor, producing garbled output (word repetitions, doubled punctuation) with temperature > 0.
Create a fresh descriptor per encode() call, matching the pattern MPSGraphArgmaxSampler already uses.