ggml : recurrent state rollback for ggml_ssm_scan (#26623)

* Initial changes for Recurrent state rollback for nemotron for cpu and cuda

* Removing CPU RS rollback. Will enable it in subsequent PRs

* addition of test case

* Removing assert and calling runtime API to check if op is supported

* removing extra API and updating the call sites for K

* replace static cuda detection to runtime fused_op api

* address review comments and fallback when SSM rollback not supprted

* Adding changes for supporting RS-rollback in CPU. Also added test-backend-ops for cpu and cuda

* removing memory manipulation as rs rollback is now supported in CPU

* removing the static probe which is not needed now

* correcting the format

* address review comments

* enabling test for all the backends, unsupported backends will fallback to CPU

* Apply suggestions from code review

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* choose different graph based on the result of fused_ssm_op is supported or not and also handled memory->n_rs_seq >1 case incase of op is not supported

* Support K > 1 in ssm_scan for all backends

* Fix CI Issues

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>
Co-authored-by: Gaurav Garg <gaugarg@nvidia.com>

ggml/src/ggml-et/et-kernels/src/ssm_scan_f32.c

@@ -12,7 +12,8 @@ struct ggml_et_ssm_scan_params {
     struct ggml_tensor src4;  // B:   [d_state, n_group, n_seq_tokens, n_seqs]
     struct ggml_tensor src5;  // C:   [d_state, n_group, n_seq_tokens, n_seqs]
     struct ggml_tensor src6;  // ids: [n_seqs] i32
-    struct ggml_tensor dst;   // packed [y, final_state]
+    struct ggml_tensor dst;   // packed [y, states]
+    int32_t            K;
 };
 
 static inline float softplus_f32(float x) {
@@ -72,6 +73,7 @@ int entry_point(struct ggml_et_ssm_scan_params * params, void * env) {
     const int64_t n_seq_tokens = src1->ne[2];
     const int64_t n_seqs       = src1->ne[3];
     const int64_t y_elems      = src1->ne[0] * src1->ne[1] * src1->ne[2] * src1->ne[3];
+    const int64_t K            = params->K;
 
     if (src0->nb[0] != sizeof(float) || src1->nb[0] != sizeof(float) || src2->nb[0] != sizeof(float) ||
         src3->nb[0] != sizeof(float) || src4->nb[0] != sizeof(float) || src5->nb[0] != sizeof(float) ||
@@ -79,7 +81,7 @@ int entry_point(struct ggml_et_ssm_scan_params * params, void * env) {
         return -1;
     }
 
-    if (n_group <= 0 || n_head % n_group != 0) {
+    if (K < 1 || n_group <= 0 || n_head % n_group != 0) {
         return -1;
     }
 
@@ -260,6 +262,15 @@ int entry_point(struct ggml_et_ssm_scan_params * params, void * env) {
                         sumf += st * C_row[state_idx];
                     }
 
+                    const int64_t slot = n_seq_tokens - 1 - token_idx;
+                    if (slot > 0 && slot < K) {
+                        float * state_snapshot =
+                            (float *) ((char *) state_dst + (size_t) slot * n_seqs * src0->nb[3]);
+                        for (int64_t i = 0; i < d_state; ++i) {
+                            state_snapshot[i] = state_dst[i];
+                        }
+                    }
+
                     dst_data[seq_idx * (n_seq_tokens * n_head * head_dim) + token_idx * (n_head * head_dim) +
                              head_idx * head_dim + dim_idx] = sumf;
                 }

ggml/src/ggml-et/ggml-et-ops.cpp

@@ -2064,6 +2064,7 @@ bool ggml_et_op_ssm_scan(ggml_backend_et_device_context * dev_ctx, const ggml_te
     params.src5 = *node->src[5];
     params.src6 = *node->src[6];
     params.dst  = *node;
+    params.K    = ggml_get_op_params_i32(node, 0);
 
     bool kernel_result = ggml_et_launch_kernel(dev_ctx, "ssm_scan_f32", &params, sizeof(params), 0xFFFFFFFF);
 

ggml/src/ggml-et/ggml-et-ops.h

@@ -218,7 +218,8 @@ struct ggml_et_ssm_scan_params {
     ggml_tensor src4;  // B:   [d_state, n_group, n_seq_tokens, n_seqs]
     ggml_tensor src5;  // C:   [d_state, n_group, n_seq_tokens, n_seqs]
     ggml_tensor src6;  // ids: [n_seqs] i32
-    ggml_tensor dst;   // [y, final_state] packed output from ggml_ssm_scan()
+    ggml_tensor dst;   // [y, states] packed output from ggml_ssm_scan()
+    int32_t     K;
 };
 
 struct ggml_et_rwkv_wkv6_params {