Add GreedySearch with only one repair schedule.

prrt/hec_search.py

@@ -102,10 +102,11 @@ class HECFullSearch(AbstractSearch):
         return residual_packet_erasure_rate
 
 
-class HECGreedySearch(AbstractSearch):
-    def __init__(self, n_p_max, prrtApplicationParameters, prrtChannelParameters, prrtSystemParameters):
+class HECReducedSpaceSearch(AbstractSearch):
+    def __init__(self, n_p_min, n_p_max, prrtApplicationParameters, prrtChannelParameters, prrtSystemParameters):
         self.n_max = 255
         self.step_size = 2 # Step size in the estimation of the optimum code word length
+        self.n_p_min = n_p_min
         self.n_p_max = n_p_max
         self.prrtApplicationParameters = prrtApplicationParameters
         self.prrtChannelParameters = prrtChannelParameters
@@ -138,7 +139,7 @@ class HECGreedySearch(AbstractSearch):
             k_max = min(self.get_k(n_c, req_delay), self.get_k_lim(1, self.n_max))
             for k in [1, k_max]:
                 n = self.estimate_n_for_k(k)
-                repair_schedules = ric.gen_repair_schedule(n - k, n_c, 1, self.n_p_max, self.is_order_ascending)
+                repair_schedules = ric.gen_repair_schedule(n - k, n_c, self.n_p_min, self.n_p_max, self.is_order_ascending)
                 for repair_schedule in repair_schedules:
                     coding_conf = prrt.PrrtCodingConfiguration(n, k, repair_schedule)
                     ri = coding_conf.get_redundant_information(self.prrtChannelParameters)
@@ -184,6 +185,97 @@ class HECGreedySearch(AbstractSearch):
 
         return 0
 
+    def residual_packet_erasure_rate(self, k, n, prrtApplicationParameters, prrtChannelParameters):
+        total_packet_erasure = 0
+        for i in range(1, k):
+            for j in range(max(n - k + 1, i), n - k + i):
+                packet_erasure_at_i = i * self.hypergeometric_distribution(n, k, i, j) * self.get_error_prob(j, n, prrtChannelParameters.loss_rate_fwd)
+                total_packet_erasure += packet_erasure_at_i
+        residual_packet_erasure_rate = (1 / k) * total_packet_erasure # Pr(k, n)
+        return residual_packet_erasure_rate
+
+class HECGreadySearch(AbstractSearch):
+    def __init__(self, n_p_min, n_p_max, prrtApplicationParameters, prrtChannelParameters, prrtSystemParameters):
+        self.n_max = 255
+        self.step_size = 2 # Step size in the estimation of the optimum code word length
+        self.n_p_min = n_p_min
+        self.n_p_max = n_p_max
+        self.prrtApplicationParameters = prrtApplicationParameters
+        self.prrtChannelParameters = prrtChannelParameters
+        self.prrtSystemParameters = prrtSystemParameters
+        self.p_t = self.prrtApplicationParameters.max_residual_loss_rate
+        self.is_order_ascending = True
+        pass
+
+    def search(self):
+        ri_opt = math.inf
+        k_opt = 0
+        n_opt = 0
+        n_p_opt = []
+        # Eq.5.9, page 125
+        fec_delay_min = self.prrtSystemParameters.source_packet_interval + \
+                        self.n_p_max * self.prrtSystemParameters.redundancy_packet_transmission_delay + \
+                        (self.prrtChannelParameters.rtt_prop_fwd + self.prrtSystemParameters.processing_delay) / 2 + \
+                        self.prrtSystemParameters.packet_loss_detection_delay
+        # Eq.5.9 page 125 assumung D_sup = 0
+        req_delay = self.prrtChannelParameters.rtt_prop_fwd + \
+                    self.n_p_max * self.prrtSystemParameters.redundancy_packet_transmission_delay + \
+                    self.prrtSystemParameters.processing_delay
+        # Eq.5.10, page 125
+        n_c_max = math.ceil((self.prrtApplicationParameters.max_latency - fec_delay_min) / req_delay)
+        # self.k_lim = somewhat(prrtApplicationParameters.loss_tolerance, self.n_max)
+
+        # n_c = 0 is the proactive packet
+        for n_c in range(n_c_max):
+            # Eq.5.11, k(Nc, D_T), page 125
+            k_max = min(self.get_k(n_c, req_delay), self.get_k_lim(1, self.n_max))
+            for k in [1, k_max]:
+                n = self.estimate_n_for_k(k)
+                repair_schedule = ric.gen_repair_schedule(n - k, n_c, self.n_p_min, self.n_p_max)
+                coding_conf = prrt.PrrtCodingConfiguration(n, k, repair_schedule)
+                ri = coding_conf.get_redundant_information(self.prrtChannelParameters)
+                if ri < ri_opt:
+                    k_opt = k
+                    n_opt = n
+                    n_p_opt = repair_schedule
+        return prrt.PrrtCodingConfiguration(n_opt, k_opt, n_p_opt)
+
+    def get_k(self, n_c, req_delay):
+        return math.ceil((self.prrtApplicationParameters.max_latency -
+                   self.n_p_max * self.prrtSystemParameters.redundancy_packet_transmission_delay -
+                   (self.prrtChannelParameters.rtt_prop_fwd + self.prrtSystemParameters.processing_delay) / 2 -
+                   self.prrtSystemParameters.packet_loss_detection_delay -
+                   n_c * req_delay) / self.prrtSystemParameters.source_packet_interval)
+
+    def get_k_lim(self, start, end):
+        mid_point = math.ceil((end - start) / 2)
+        p_r = self.get_max_coding_block_length(mid_point)
+        if p_r == self.p_t:
+            return mid_point
+        elif p_r  > self.p_t:
+            self.get_k_lim(start, mid_point - 1)
+        else:
+            self.get_k_lim(mid_point + 1, end)
+
+    # Pr(k, n_max)
+    def get_max_coding_block_length(self, k):
+        total_packet_erasure = 0
+        for i in range(1, k):
+            for j in range(max(self.n_max - k + 1, i), self.n_max - k + i):
+                packet_erasure_at_i = i * self.hypergeometric_distribution(self.n_max, k, i, j) * self.get_error_prob(
+                    j, self.n_max, self.prrtChannelParameters.loss_rate_fwd)
+                total_packet_erasure += packet_erasure_at_i
+        return (1 / k) * total_packet_erasure
+
+    def estimate_n_for_k(self, k):
+        n = k + 1
+        while self.residual_packet_erasure_rate(k, n, self.prrtApplicationParameters, self.prrtChannelParameters) > self.prrtApplicationParameters.max_residual_loss_rate\
+                and n <= self.n_max - self.step_size:
+
+            print("")
+
+        return 0
+
     def residual_packet_erasure_rate(self, k, n, prrtApplicationParameters, prrtChannelParameters):
         total_packet_erasure = 0
         for i in range(1, k):

prrt/ric.pyx

@@ -20,7 +20,7 @@ def generate_restricted_integer_compositions(redundancy, positions, min, max):
                 yield (i,) + result
 
 # is_order_ascending = False for full search and True for greedy search
-def gen_repair_schedule(redundancy, positions, min, max, is_order_ascending):
+def gen_repair_schedules(redundancy, positions, min, max, is_order_ascending):
     arbitrary_schedules = []
     ordered_schedules = set()
 
@@ -33,4 +33,20 @@ def gen_repair_schedule(redundancy, positions, min, max, is_order_ascending):
             ordered_schedules.append(itertools.permutations(i))
         return list(ordered_schedules)
     else:
-        return arbitrary_schedules
\ No newline at end of file
+        return arbitrary_schedules
+
+
+def gen_repair_schedule(redundancy, positions, min, max):
+	if(redundancy < positions * min or min > max):
+		raise Exception("Illegal input combinations. Make sure the min > max. And, number of total redundancy is greater that positions*min.")
+	opt_schedule = [min for p in range(positions)]
+	redundancy_left_over = redundancy - min * positions
+	last_index = positions - 1
+	while(redundancy_left_over > 0):
+		if(opt_schedule[last_index] < max):
+			opt_schedule[last_index] += 1
+			redundancy_left_over -= 1
+		else:
+			last_index -= 1
+
+	return opt_schedule
\ No newline at end of file