Improve documentation (#2006)

* Add comment on proof-mode extra step

* Add comment on temporary segments

* Update vm/src/vm/vm_memory/memory.rs

Co-authored-by: fmoletta <[email protected]>

* Update vm/src/vm/vm_memory/memory.rs

Co-authored-by: fmoletta <[email protected]>

* Update vm/src/vm/vm_memory/memory.rs

Co-authored-by: Franco Giachetta <[email protected]>

---------

Co-authored-by: fmoletta <[email protected]>
Co-authored-by: Franco Giachetta <[email protected]>

Author: 3 people

vm/src/cairo_run.rs

@@ -95,6 +95,8 @@ pub fn cairo_run_program_with_initial_scope(
         .map_err(|err| VmException::from_vm_error(&cairo_runner, err))?;
 
     if cairo_run_config.proof_mode {
+        // we run an additional step to ensure that `end` is the last step execute,
+        // rather than the one after it.
         cairo_runner.run_for_steps(1, hint_processor)?;
     }
     cairo_runner.end_run(

vm/src/vm/vm_memory/memory.rs

@@ -158,6 +158,11 @@ impl AddressSet {
 
 pub struct Memory {
     pub(crate) data: Vec<Vec<MemoryCell>>,
+    /// Temporary segments are used when it's necessary to write data, but we
+    /// don't know yet where it will be located. These segments will eventually
+    /// be relocated to the main memory according to the `relocation_rules`. For
+    /// example, dictionaries are required to be contiguous, so each is stored in a
+    /// temporary segment and eventually relocated to a single segment.
     pub(crate) temp_data: Vec<Vec<MemoryCell>>,
     // relocation_rules's keys map to temp_data's indices and therefore begin at
     // zero; that is, segment_index = -1 maps to key 0, -2 to key 1...