fix(kernels): remove global --use_fast_math; selective per-kernel intrinsics only (T3.1) - #143
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…max only (T3.1) Drop --use_fast_math from NVCC_FLAGS: the flag swapped every expf/tanhf/logf/division for unsafe approximations library-wide; the non-saturating fast tanhf caused the GELU blowup behind the GPU f32 CrossAsset cliff (ztensor#125). Per the torch numerics convention (zerfoo plan-gpu-training-hardening T3.1) fast intrinsics are now re-enabled selectively in kernel source, only where the PyTorch-oracle gate proves equivalence within tolerance: - kernel_softmax keeps __expf AFTER max-subtraction (argument <= 0, result in (0,1], ~2^-21 relative error -- inside the Softmax tolerance atol 1e-6 / rtol 1e-4). - Everything else gets the accurate libdevice functions. - The tanh saturation clamp (ztensor#125) is RETAINED as defense-in-depth. Gate plumbing: oracle-gen grows -engine gpu (GenerateAllWith records compute.GPUEngine bundles through the same format -- the GPU-side oracle gate the scripts/oracle README reserved for T3.x), and compute/gpu_kernel_bench_test.go adds per-kernel GPU micro-benchmarks for the ops whose codegen changed, for the before/after perf delta. Verifies zerfoo UC-GH-5.
…, perf delta within noise
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Linear re-roll of #142 (same content; #142 grew a merge commit resolving the T2.4 devlog conflict, which GitHub's rebase-merge refuses to replay). All GB10 evidence lives on #142:
__expffwd max_rel 1.4e-7 (tol 1e-4); Tanh exact.VALIDATION_OK_new2, podztensor-t31-gate-new2-dbcb0da).Implements zerfoo plan-gpu-training-hardening T3.1 + S3.1.1 (verifies UC-GH-5).
ztensor-t31-build-393d8eb)