openfam::fam::fam_max

Atomically replace a value in FAM with the maximum of it and some given value.

Synopsis

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, int32_t value);

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, int64_t value);

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, uint32_t value);

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, uint64_t value);

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, float value);

void fam_max(Fam_Descriptor *descriptor, uint64_t offset, double value);

Description

These methods atomically replace a value in FAM with the maximum of the value given and the existing value.

Input Arguments

Name	Description
descriptor	Descriptor associated with the data item.
Offset	Offset within the data item in FAM where value is located.
Value	Value to be compared to the existing value at the given location.

Return Values

None. Throws an exception on error.

Exceptions

Exception	Description
Fam_InvalidOption_Exception	incorrect parameters are passed.
Fam_Datapath_Exception	error occurred during atomic operation over fabric.
FAM_ERR_NOPERM	Caller does not have access rights.
FAM_ERR_LIBFABRIC	libfabric error occurred.
FAM_ERR_NOTFOUND	Item not found in the region.
FAM_ERR_GRPC	if there is a communication error with memory server
FAM_ERR_RPC_CLIENT_NOTFOUND	Memory server initialization failure

Notes

These methods atomically replace a value in FAM with the larger of the existing value and the value given in the method. Note that the offset argument must point to the correct value for the data type. Availability of these methods is dependent on hardware support for the operations.

A subsequent successful completion of fam_quiet() call ensures the completion of this atomic operation.

Example

#include <string.h>
#include <fam/fam.h>
#include <fam/fam_exception.h>
using namespace std;
using namespace openfam;

int main(void) {
	fam *myFam = new fam();
	 // ... Initialization code here
	 try {
		// look up the descriptor to a previously allocated data item
		// (an integer array with at least 10 elements)
		Fam_Descriptor *descriptor = myFam->fam_lookup("myItem", "myRegion");
	
		//Atomically set the maximum value for the first integer element in the array
		myFam->fam_max(descriptor, 0, 100);
	
		// ensure that the max operation is complete
		myFam->fam_quiet();
	
		// The first integer in FAM is now the maximum of its previous value and 100
	 } catch (Fam_Exception &e) {
		printf("fam API failed: %d: %s\n", e.fam_error(), e.fam_error_msg());
	 }

	 // ... Finalization code follows
}