Removes dropout-related fields from Flash_fwd_params

Cleans up the parameter structure by removing unused dropout probability fields, scaling factors, random state management, and rotary interleaving flag.

Moves softcap field to improve struct organization and readability.

Author: LoserCheems

csrc/src/flash.h

@@ -93,6 +93,7 @@ struct Flash_fwd_params : public QKV_params, public Mask_params, public Bias_par
     // The scaling factors for the kernel.
     float scale_softmax;
     float scale_softmax_log2;
+    float softcap;
 
     // array of length b+1 holding starting offset of each sequence.
     int * __restrict__ cu_seqlens_q;
@@ -128,32 +129,13 @@ struct Flash_fwd_params : public QKV_params, public Mask_params, public Bias_par
     index_t block_table_batch_stride;
     int page_block_size;
 
-    // The dropout probability (probability of keeping an activation).
-    float p_dropout;
-    // uint32_t p_dropout_in_uint;
-    // uint16_t p_dropout_in_uint16_t;
-    uint8_t p_dropout_in_uint8_t;
-
-    // Scale factor of 1 / (1 - p_dropout).
-    float rp_dropout;
-    float scale_softmax_rp_dropout;
-    float softcap;
-
-    // Random state.
-    at::PhiloxCudaState philox_args;
-
-    // Pointer to the RNG seed (idx 0) and offset (idx 1).
-    uint64_t * rng_state;
-
     bool is_bf16;
     bool is_causal;
 
     // If is_seqlens_k_cumulative, then seqlen_k is cu_seqlens_k[bidb + 1] - cu_seqlens_k[bidb].
     // Otherwise it's cu_seqlens_k[bidb], i.e., we use cu_seqlens_k to store the sequence lengths of K.
     bool is_seqlens_k_cumulative;
 
-    bool is_rotary_interleaved;
-
     int num_splits;  // For split-KV version
 
     bool unpadded_lse;  // For varlen paths: LSE is in [nheads, total_seqlen_q] format instead of [b, nheads, seqlen_q].