update SVRG gradient

main.py

@@ -15,6 +15,7 @@
 from petric import Dataset
 from sirf.contrib.partitioner import partitioner
 import numpy as np
+import numbers
 
 assert issubclass(ISTA, Algorithm)
 
@@ -24,7 +25,8 @@ def __init__(self, functions, sampler=None, snapshot_update_interval=None, store
                  init_steps=0, **kwargs):
 
         super(FullGradientInitialiserFunction, self).__init__(functions, sampler=sampler, 
-                                                              snapshot_update_interval=snapshot_update_interval, store_gradients=store_gradients, **kwargs)
+                                                              snapshot_update_interval=snapshot_update_interval, 
+                                                              store_gradients=store_gradients, **kwargs)
         self.counter = 0
         self.init_steps = init_steps
 
@@ -46,11 +48,19 @@ def gradient(self, x, out=None):
             self.counter += 1
             return self.full_gradient(x, out=out)
 
-        self.function_num = self.sampler.next()
-
-        self._update_data_passes_indices([self.function_num])
-
-        return self.approximate_gradient(x, self.function_num, out=out)
+        if ( (self.snapshot_update_interval != 0) and (self._svrg_iter_number % (self.snapshot_update_interval)) == 0):
+
+            return self._update_full_gradient_and_return(x, out=out)
+
+        else:
+
+            self.function_num = self.sampler.next()
+            if not isinstance(self.function_num, numbers.Number):
+                raise ValueError("Batch gradient is not yet implemented")
+            if self.function_num >= self.num_functions or self.function_num < 0:
+                raise IndexError(
+                    f"The sampler has produced the index {self.function_num} which does not match the expected range of available functions to sample from. Please ensure your sampler only selects from [0,1,...,len(functions)-1] ")
+            return self.approximate_gradient(x, self.function_num, out=out)
 
 class BSREMPreconditioner(Preconditioner):
     '''
@@ -251,4 +261,4 @@ def __init__(self, data: Dataset, update_objective_interval=10):
         super().__init__(initial=data.OSEM_image, f=f, g=g, step_size=step_size_rule, 
                          preconditioner=preconditioner, update_objective_interval=update_objective_interval)
 
-submission_callbacks = []
+submission_callbacks = []  # 10000 iterations max