[wip] Request compute units for price update transactions (#301)

* compute budget

* hex

* Flip endianness

Co-authored-by: Jayant Krishnamurthy <[email protected]>
Co-authored-by: Tom Pointon <[email protected]>

Author: 3 people

pc/rpc_client.cpp

@@ -910,19 +910,29 @@ bool rpc::upd_price::build_tx(
   auto& first = *upds[ 0 ];
 
   // accounts
-  tx.add_len( n + 3 ); // n + 3 accounts: publish, symbol{n}, sysvar, program
+  tx.add_len( n + 4 ); // n + 4 accounts: publish, symbol{n}, sysvar, pyth program, compute budget program
   tx.add( *first.pkey_ ); // publish account
   for ( unsigned i = 0; i < n; ++i ) {
     tx.add( *upds[ i ]->akey_ ); // symbol account
   }
   tx.add( *(pub_key*)sysvar_clock ); // sysvar account
   tx.add( *first.gkey_ ); // programid
+  tx.add( *(pub_key*)compute_budget_program_id ); // compute budget program id
 
   // recent block hash
   tx.add( *first.bhash_ ); // recent block hash
 
   // instructions section
-  tx.add_len( n ); // n instruction(s)
+  tx.add_len( n + 1 ); // 1 compute limit instruction, n upd_price instruction(s)
+
+  // Set compute limit
+  tx.add( (uint8_t)( n + 3 ) ); // compute budget program id index in accounts list
+  tx.add_len<0>(); // no accounts
+  // compute limit instruction parameters
+  tx.add_len<sizeof(uint8_t) + sizeof(uint32_t)>(); // uint8_t enum variant + uint32_t requested compute units
+  tx.add( (uint8_t) 2 ); // SetComputeLimit enum variant
+  tx.add( (uint32_t) CU_BUDGET_PER_IX * n ); // the budget (scaled for number of instructions)
+
   for ( unsigned i = 0; i < n; ++i ) {
     tx.add( (uint8_t)( n + 2 ) ); // program_id index
     tx.add_len< 3 >(); // 3 accounts: publish, symbol, sysvar

program/c/src/oracle/oracle.h

@@ -53,6 +53,11 @@ const uint64_t EXTRA_PUBLISHER_SPACE = 3072ULL;
 #define PC_ACCTYPE_TEST       4
 #define PC_ACCTYPE_PERMISSIONS       5
 
+
+// Compute budget requested per price update instruction
+// The biggest instruction appears to be about ~10300 CUs, so overestimate by 100%.
+#define CU_BUDGET_PER_IX 20000
+
 // binary version of sysvar_clock account id
 const uint64_t sysvar_clock[] = {
   0xc974c71817d5a706UL,
@@ -61,6 +66,21 @@ const uint64_t sysvar_clock[] = {
   0x215b5573UL
 };
 
+// compute budget program id in hex (but wrong endianness)
+/*
+321721e56f460603
+e79bc372baadecff
+6b12f7c5bbe58cbc
+403a9b432c
+*/
+
+const uint64_t compute_budget_program_id[] = {
+  0x321721e56f460603UL,
+  0xe79bc372baadecffUL,
+  0x6b12f7c5bbe58cbcUL,
+  0x403a9b432cUL
+};
+
 // public key of symbol or publisher account
 typedef union pc_pub_key
 {