[GNA] For similar records, the pattern length was increased to 4 in t…

…he algorithm for determining infinite cycles. (openvinotoolkit#7165)

* for similar records, the pattern length was increased to 4

* Added comments

inference-engine/src/gna_plugin/frontend/model_quantizer.hpp

@@ -115,7 +115,8 @@ class ModelQuantizer {
                 }
             }
 
-            // looking for infinite loop by using algorithm of compute prefix function, complexity O(N)
+            // We are looking for infinite loop by using algorithm of compute prefix function, complexity O(N)
+            // (a part of the Knuth–Morris–Pratt algorithm).
             std::map<int, int> prefixFunction;
             int k = infiniteLoopHistory.size();
             for (int i = infiniteLoopHistory.size() - 2; i >= 0; i--) {
@@ -128,12 +129,36 @@ class ModelQuantizer {
                     k--;
                 }
 
-                if ((infiniteLoopHistory.size() - i) % 2 == 0 && (infiniteLoopHistory.size() - i) / 2 == infiniteLoopHistory.size() - k) {
+                // The pattern length is a length of a repeating string sequence (it is 2 in the example below).
+                // concat_14_input_0_reshape#concat_15
+                // concat_15_input_1_reshape#add_12
+                // add_12#Add_16
+                // Reshape_41#add_12
+                // add_12#Add_16
+                // Reshape_41#add_12
+                //
+                // In the case of pattern length is 1, an infinite loop can be found on 2 consecutive strings.
+                // To avoid this, we will expect the appearance of 4 equal strings for the case pattern length is 1.
+                if ((infiniteLoopHistory.size() - i) % 2 == 0 &&
+                    (infiniteLoopHistory.size() - i) / 2 == infiniteLoopHistory.size() - k &&
+                    ((infiniteLoopHistory.size() - i) / 2 > 1 ||
+                        std::distance(infiniteLoopHistory.rbegin(),
+                            std::find_if_not(infiniteLoopHistory.rbegin(), infiniteLoopHistory.rend(),
+                                [&infiniteLoopHistory](const std::string& str) { return str == infiniteLoopHistory.back(); })) > 3)) {
+                    gnalog() << "infiniteLoopPattern:\n";
+                    for (const auto& s : infiniteLoopPattern) {
+                        gnalog() << "\t " << s << '\n';
+                    }
                     infiniteLoopPattern.clear();
-                    int patternLength = (infiniteLoopHistory.size() - i)/2;
+                    int patternLength = (infiniteLoopHistory.size() - i) / 2;
+                    gnalog() << "patternLength: " << patternLength << '\n';
                     for (int j = 0; j < patternLength; j++) {
                         infiniteLoopPattern.emplace_back(infiniteLoopHistory[infiniteLoopHistory.size() - patternLength + j]);
                     }
+                    gnalog() << "infiniteLoopHistory:\n";
+                    for (const auto& s : infiniteLoopHistory) {
+                        gnalog() << "\t " << s << '\n';
+                    }
                     infiniteLoopHistory.clear();
                     gnalog() << "infinite loop detected\n";
                     break;