added changes on checking similarity

base/api/haystackmapper.py

@@ -0,0 +1,65 @@
+from .haystack import haystack
+
+
+# class haystackmapper:
+    
+#     """
+#     haystackmapper is a class responsible for map process, 
+#     it emits key-value pair if a needle can be found in the haystack
+#     (key: haystack name, value: 1 represents a match)
+#     """
+    
+#     emission = []
+#     def __init__ (self, haystacks):
+#         self.haystacks = haystacks
+def mapper (stack, needle):
+    len_needle = len(needle)
+    emission = []
+    for haystack in stack:
+        len_haystack = haystack.get_length()
+        data = haystack.get_data()
+        for i in range(len_haystack):
+                
+            #get subsequence length
+            len_sub = min(len_needle, (len_haystack - i)) 
+            
+            subsequence = data[i:i + len_needle]
+            nomatch = 0
+            """ 
+            Uncomment this for debugging:                 
+            #difference = []
+            """
+            
+            if len_sub <= 1:
+                nomatch = 1
+                break
+            for i in range(len_sub): # len_sub <= len_needle
+                """ 
+                Uncomment this for debugging: 
+                if abs(needle[i]) > 100 :
+                    difference.append(abs(subsequence[i] - needle[i])/needle[i] )
+                else:
+                    difference.append(0)
+                """
+                if abs(needle[i]) > 100 and abs(subsequence[i] - needle[i]) > abs(0.05*needle[i]): 
+                    # allow slight variation
+                    nomatch = 1
+                    break
+            
+            if nomatch == 0:
+                
+                """ 
+                Uncomment this section for deubgging to show comparison
+                print(needle)
+                print(subsequence)
+                print(difference)
+                print(haystack.get_name(),nomatch)
+                """
+                
+                emission.append([haystack.get_name(), 1])
+                break
+            else:
+                pass
+    
+    return emission
+