Incidentally, exploring swarm intelligence isn't terribly difficult if you know a bit of programming... when I was experimenting with it, I just used VBA and Excel. The trick is knowing object oriented programming and using it to create multiple entities that can interact in a virtual environment - e.g., by position on a 2 dimensional matrix. Excel's main advantage is that its easy to dump the results out into a worksheet to examine and graph, though I wouldn't use it for any computationally heavy project. Because the behavior of your entities is based on simple rules, the programming can be as basic as checking if the block in an array at the position ahead or behind is occupied, and then altering behavior accordingly... or assessing the values of the other members of the swarm and modifying its status in response.
It would be nice if I could point to a bespoke programming environment for programming and experimenting with these concepts... I suspect with some looking I could find one, but it would probably be locked away in some university comp sci lab. I did find reference to this book which has a chapter on swarm intelligence and some pseudocode to start people out with however.
Showing posts with label fish. Show all posts
Showing posts with label fish. Show all posts
Sunday, 2 February 2014
Swarm Intelligence and Data Mining
Some years ago, I experimented with swarm intelligence as a way to search out optimal solutions for non-linear problems. The idea behind this is that rather than taking a straight computational approach, you use a swam of entities that 'search' the computational space for the optimal solution, each entity following a set of search rules and communicating with the other entities in order to quickly find the best result. Its used for problems where there may be multiple 'sorta right' answers and where its easy to get an answer that is better than the others, but not the best possible answer. Think of problems such as the travelling salesman problem, where the is one best solution, but it could take a long time to find it, and there are lots of suboptimal solutions that look right (better than most) but aren't the best.
The inspiration for this approach is taken directly from nature... ants are an obvious type of animal that uses swarm intelligence, as are flocking birds and schooling fishes. Using simple rules of proximity, they maintain a structure and move as a unit (or in the case of ants, move towards a goal) without an overarching intelligence. On this video below, look at the way these grunts change their movement and shift direction together as I swim through the school... they do it almost automatically, with no pauses to reassess their location and speed. Imagine trying to do this if you were driving in a 'swarm' of cars... without the instinct to automatically judge neighbors distance and adjust speed and direction, it would be a disaster.
Monday, 3 October 2011
Wheres Waldo underwater
Can you find the Painted Gobies (Pomatoschistus pictus) in this picture? (Taken at the Farnes, Sept 17, approx 20m depth).
(hint - click on the photograph to enlarge)
Thursday, 21 July 2011
Thursday, 30 December 2010
Free flow
You've trained for this sort of thing, sure... in that warm swimming pool, kneeling around the instructor, the surface an undulating mirror a few feet above your head. Hold the button down on your regs, pretend its jammed, and as the air flows around you, take breaths from one side and let the excess stream past. Don't panic, you can still get air... just head to the surface and swim back to the boat. Just one more safety lesson they will teach you, one more you'll soon forget as you swim through multi-hued reefs and watch the myriad displays of sea life dance around you. Besides, you'll hear frequently that most regulator free flows take place on the surface, at sub-zero temperatures, not underwater in warm tropical seas.
And who in their right mind would be diving in sub-zero weather?
Our goal was simple... drop down to the bottom , take a bearing at the sunken airplane, then head off at 145 degrees until we reached the gnome garden. My buddy would navigate, I would be running the camera - not at anything special, but I wanted to try capturing a continuous film of a dive, rather than my usual 30 second clips of an interesting fish or curious lobster. The quarry with its limited distractions seemed as good a place as any to try and I had never been to the gnome garden before... and the cold weather? Well, it promised a swim free of other divers, and hopefully a bit less of the algae that clouded the waters each summer.
Ten minutes in, and we have problems. Free flows may be more common at the surface, but in water only a few degrees above freezing they can happen at any depth. At that moment we were 15 meters below the surface and my buddy was engulfed in a column of bubbles as his regs vented precious air. This shouldn't be a problem... we are trained what to do, after all, but quarry diving in winter adds a few extra dimensions not covered in the training courses I took years ago. The first problem is the venting regulator - not only is it depleting my buddies air, but the bubbles are blocking his vision and threatening to knock free his mask - the last thing he needs is the shock of ice-cold water hitting his face if his mask comes free. Taking off your mask in warm water is an unpleasant enough experience - when the water is three degrees I would challenge anyone not to panic. This time, at least, luck is on our side, and he could switch to the spare reg on his pony bottle (a christmas gift - who would have thought he would need it so soon?) but with air going fast we needed to get to the surface.
The second problem of diving in cold water is that to even be in the water safely you need a dry suit. A dry suit is basically a bag of air that surrounds you, and much of the art of dry suit diving is learning to manage that bag of air so that you don't go shooting to the surface like a balloon. This is accomplished by carrying large amounts of lead (15 kilos, in my case) to counteract both natural boyancy and the boyancy of the air in the dry suit. Without a bit of air in the dry suit, one has a tendancy to go to the bottom. Even with a secondary air supply, my buddy still needed air to control his ascent and to stay on the surface. With thick gloves and frigid hands, creative solutions such as shutting off his main tank until we surfaced were out of the question.
Surfacing in murky water is harder than it sounds... you have no reference points, no sight of ground below or the surface above, only your depth gauge or dive computer to tell you where you are. You don't want to go straight up - that risks the bends - but with a limited air supply, patience isn't a virtue. I think we spent the first 30 seconds finning away before we realized we weren't going anywhere - just bobbing back and forth a few meters above the ground. Guided by the depth display on our computers, we slowly made our ascent to six meters, before my buddy signalled for us to halt our ascent, giving me the sign for a three minute decompression stop. I was a bit surprised - ten minutes at 15 meters isn't long enough to need a safety stop - and the gauge for his tank was still dropping. The back-up air supply had given him a bit of confidence - but maybe a bit too much - it couldn't inflate his boyancy jacket and with only a small air supply, he couldn't have had more than a few minutes left on his reserve. Still... what could I do? So there we were, hanging about at 6 meters, a stream of bubbles pouring from the regulator dangling at his side, while his gauge dropped into the red and I wondered when his pony tank would run out. A minute and a half in, and I finally decide enough is enough - the surface was in sight, but any longer dallying about and he would never reach it. An executive descision had to be made. Grabbing his jacket, I signalled upwards and began my final ascent, lifting him with me. Only at the surface, his jacket now inflated with the last wisps of his air, could I finally relax.
The long wait at 6 meters seemed to me a bit silly, given the circumstances, but it could have been different. If we had been down longer, or deeper, a straight run to the surface could have had much more dire consequences... there is a reason that novice divers are told not to go below 18 meters, where optional stops become mandatory and the surface may as well be a hundred meters away for all that you can safely flee to it.
And as for my attempt at filming? Turns out my camera has difficulties at cold temperatures.
I guess for now, its another 30 second short feature.
And who in their right mind would be diving in sub-zero weather?
Our goal was simple... drop down to the bottom , take a bearing at the sunken airplane, then head off at 145 degrees until we reached the gnome garden. My buddy would navigate, I would be running the camera - not at anything special, but I wanted to try capturing a continuous film of a dive, rather than my usual 30 second clips of an interesting fish or curious lobster. The quarry with its limited distractions seemed as good a place as any to try and I had never been to the gnome garden before... and the cold weather? Well, it promised a swim free of other divers, and hopefully a bit less of the algae that clouded the waters each summer.
Ten minutes in, and we have problems. Free flows may be more common at the surface, but in water only a few degrees above freezing they can happen at any depth. At that moment we were 15 meters below the surface and my buddy was engulfed in a column of bubbles as his regs vented precious air. This shouldn't be a problem... we are trained what to do, after all, but quarry diving in winter adds a few extra dimensions not covered in the training courses I took years ago. The first problem is the venting regulator - not only is it depleting my buddies air, but the bubbles are blocking his vision and threatening to knock free his mask - the last thing he needs is the shock of ice-cold water hitting his face if his mask comes free. Taking off your mask in warm water is an unpleasant enough experience - when the water is three degrees I would challenge anyone not to panic. This time, at least, luck is on our side, and he could switch to the spare reg on his pony bottle (a christmas gift - who would have thought he would need it so soon?) but with air going fast we needed to get to the surface.
The second problem of diving in cold water is that to even be in the water safely you need a dry suit. A dry suit is basically a bag of air that surrounds you, and much of the art of dry suit diving is learning to manage that bag of air so that you don't go shooting to the surface like a balloon. This is accomplished by carrying large amounts of lead (15 kilos, in my case) to counteract both natural boyancy and the boyancy of the air in the dry suit. Without a bit of air in the dry suit, one has a tendancy to go to the bottom. Even with a secondary air supply, my buddy still needed air to control his ascent and to stay on the surface. With thick gloves and frigid hands, creative solutions such as shutting off his main tank until we surfaced were out of the question.
Surfacing in murky water is harder than it sounds... you have no reference points, no sight of ground below or the surface above, only your depth gauge or dive computer to tell you where you are. You don't want to go straight up - that risks the bends - but with a limited air supply, patience isn't a virtue. I think we spent the first 30 seconds finning away before we realized we weren't going anywhere - just bobbing back and forth a few meters above the ground. Guided by the depth display on our computers, we slowly made our ascent to six meters, before my buddy signalled for us to halt our ascent, giving me the sign for a three minute decompression stop. I was a bit surprised - ten minutes at 15 meters isn't long enough to need a safety stop - and the gauge for his tank was still dropping. The back-up air supply had given him a bit of confidence - but maybe a bit too much - it couldn't inflate his boyancy jacket and with only a small air supply, he couldn't have had more than a few minutes left on his reserve. Still... what could I do? So there we were, hanging about at 6 meters, a stream of bubbles pouring from the regulator dangling at his side, while his gauge dropped into the red and I wondered when his pony tank would run out. A minute and a half in, and I finally decide enough is enough - the surface was in sight, but any longer dallying about and he would never reach it. An executive descision had to be made. Grabbing his jacket, I signalled upwards and began my final ascent, lifting him with me. Only at the surface, his jacket now inflated with the last wisps of his air, could I finally relax.
The long wait at 6 meters seemed to me a bit silly, given the circumstances, but it could have been different. If we had been down longer, or deeper, a straight run to the surface could have had much more dire consequences... there is a reason that novice divers are told not to go below 18 meters, where optional stops become mandatory and the surface may as well be a hundred meters away for all that you can safely flee to it.
And as for my attempt at filming? Turns out my camera has difficulties at cold temperatures.
I guess for now, its another 30 second short feature.
Sunday, 19 September 2010
A well stocked table
The mediterranean isn't known for its diversity of life... you won't find the vast array of colorful fish that inhabit the reefs of the Red Sea, nor will you see the complex habitats of the North Atlantic kelp forests. Much of the inshore western mediterranean is composed of vast lawns of sea grass interspersed with rocks and the occasional wreck, and supports a limited range of sea life. The med has undergone several cycles of drying out, and the sea life within it represent the descendents of a relatively recent recolonization over the last 5 million years.
One advantage of this reduced diversity is that when you are in the med, rather than being distracted by a variety of fish, you can pay more attention to what they are actually doing. One interesting behavior I noted was of clusters of seabream and wrasse feeding on the rocks... the smaller Rainbow Wrasse and Ornate Wrasse would hover around the larger seabream and Ocellated Wrasse, letting them do the heavy lifting of tearing chunks of algae and encrustations off the rocks, before diving at the debris cloud to grab any interesting food morsels that were shaken free.
You can see some of this behavior in the first half of the clip below, where off to the right several small wrasse are diving through one such cloud of debris, from where a seabream has pulled away some of the encrustations. Near the end of the clip is a different behavior - a watchful Painted Comber assessing my intentions before deciding that discretion is the better part of valour and fleeing into a nearby cranny.
For those interested in which fish is which, the two larger fish in the above photos are the White Seabream (oval with one tail spot) and Two-Banded Seabream (oval with two stripes), while the Ocellated Wrasse is the large wrasse with a small spot near the tail. There are two species of smaller wrasse in the photos and movies - the wrasse with a red stripe interrupted by a black bar is a male Mediterranean Rainbow Wrasse, while the female of the species has the dark upper body and light colored underside. The orange wrasse with the light bands and black spot near its back is an Ornate Wrasse.
One advantage of this reduced diversity is that when you are in the med, rather than being distracted by a variety of fish, you can pay more attention to what they are actually doing. One interesting behavior I noted was of clusters of seabream and wrasse feeding on the rocks... the smaller Rainbow Wrasse and Ornate Wrasse would hover around the larger seabream and Ocellated Wrasse, letting them do the heavy lifting of tearing chunks of algae and encrustations off the rocks, before diving at the debris cloud to grab any interesting food morsels that were shaken free.
You can see some of this behavior in the first half of the clip below, where off to the right several small wrasse are diving through one such cloud of debris, from where a seabream has pulled away some of the encrustations. Near the end of the clip is a different behavior - a watchful Painted Comber assessing my intentions before deciding that discretion is the better part of valour and fleeing into a nearby cranny.
For those interested in which fish is which, the two larger fish in the above photos are the White Seabream (oval with one tail spot) and Two-Banded Seabream (oval with two stripes), while the Ocellated Wrasse is the large wrasse with a small spot near the tail. There are two species of smaller wrasse in the photos and movies - the wrasse with a red stripe interrupted by a black bar is a male Mediterranean Rainbow Wrasse, while the female of the species has the dark upper body and light colored underside. The orange wrasse with the light bands and black spot near its back is an Ornate Wrasse.
Wednesday, 15 September 2010
Seabream
I have to wonder what was going through the mind of this saddled seabream as I came up behind it.
These fish were surprisingly calm around divers, though if you got too close they would move away. I suppose there hasn't been much natural selection favouring a flight response from large, ungainly sea creatures streaming bubbles and making regular rasping noises, but more likely it just isn't worth the effort to flee from every large creature in the ocean... a truly timid pelagic fish would be a very exhausted fish and not one to contribute to the next generation.
A side view of one of these fish. The latin name is Oblada melanura. (as an aside, I need to get some better identification guides for the mediterranean... I have one very old guide, and the pictures in it don't do the live fish justice.)
These fish were surprisingly calm around divers, though if you got too close they would move away. I suppose there hasn't been much natural selection favouring a flight response from large, ungainly sea creatures streaming bubbles and making regular rasping noises, but more likely it just isn't worth the effort to flee from every large creature in the ocean... a truly timid pelagic fish would be a very exhausted fish and not one to contribute to the next generation.
A side view of one of these fish. The latin name is Oblada melanura. (as an aside, I need to get some better identification guides for the mediterranean... I have one very old guide, and the pictures in it don't do the live fish justice.)
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